Applications of Technology in Wine Production - ACS Symposium

Chapter 8

Applications of Technology in Wine Production Richard P. Vine

Downloaded by UNIV OF NORTH CAROLINA on June 14, 2013 | http://pubs.acs.org Publication Date: August 23, 1993 | doi: 10.1021/bk-1993-0536.ch008

Department of Food Sciences, Purdue University, West Lafayette, IN 47907

The more recently created body of s c i e n t i f i c wine knowledge supports a current technology that i s significantly different from the conventional wisdom employed by vintners even less than a decade ago. Rationale now exists to j u s t i f y new methods in virtually every phase of wine production. This chapter w i l l consider some of the more important developments that have surfaced i n the enology d i s c i p l i n e and are currently applied i n the wine industry. Optimal M a t u r i t y o f Qrapes Some commercial winemakers continue t o monitor s o l u b l e s o l i d s , i n t h e form of B r i x measurement, as t h e p r i n c i p a l grape r i p e n e s s i n d i c a t o r . Others have adopted one o f s e v e r a l formulae i n which pH and t o t a l t i t r a t a b l e a c i d i t y analyses a r e f a c t o r e d i n a r a t i o devised t o p r e d i c t optimal maturity. Robredo (8) conducted a study i n which data gathered from these t r a d i t i o n a l harvest analyses were taken i n tandem with f i n i t e HPLC measurements o f important f l a v o r compounds. The o b j e c t i v e was t o assemble a biochemical model t h a t could be used t o e s t a b l i s h more e x a c t i n g parameters i n d e c l a r i n g i d e a l grape maturation. The methodology was t o q u a n t i f y i n d i v i d u a l sugars and o r g a n i c a c i d s i n grapes which i n f l u e n c e B r i x , T.A., and pH, along with s p e c i f i c e s t e r precursors and phenols. One white and one r e d v a r i e t y were analyzed a t d i f f e r e n t times d u r i n g the r i p e n i n g process and r e s u l t s were c o r r e l a t e d with wines t h a t achieved s u p e r i o r sensory scores. The c o n c l u s i o n was t h a t t r a d i t i o n a l analyses i n d i c a t e d an optimal • i n d u s t r i a l harvest date f o r the white v a r i e t y a t l e a s t two days l a t e r than the optimal ' t e c h n i c a l h a r v e s t 1

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0097-6156/93/0536-0132$06.00A) © 1993 American Chemical Society

In Beer and Wine Production; Gump, B., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.


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time determined from the new a n a l y t i c a l p r o f i l e . The optimal i n d u s t r i a l and t e c h n i c a l harvest dates f o r the r e d v a r i e t y were t h e same. The p r a c t i c a l a p p l i c a t i o n of t h i s technology remains for the future. HPLC requirements f o r t h i s type o f c o n t r o l a r e c u r r e n t l y out of reach by most v i n t n e r s although technology i s a l s o r a p i d l y c l o s i n g t h i s gap. Some u n i v e r s i t i e s and other i n s t i t u t i o n s may be a b l e t o o f f e r interim assistance to vintners interested i n t h i s new element of q u a l i t y assurance. More p r e c i s e sampling techniques i n the vineyard w i l l a l s o be needed t o ensure accurate p r e d i c t i o n s . In t h e meantime, there a l s o remains t h e need f o r f u r t h e r r e s e a r c h t o determine optimal organic c o n s t i t u e n t p r o f i l e s f o r other grape v a r i e t i e s i n v a r i o u s e n v i r o n s . Research i n this v e i n may a l s o i d e n t i f y specific c o n s t i t u e n c y r e l a t i o n s h i p s which can enhance c e r t a i n p r o d u c t i o n parameters, such as maximizing s t a b i l i t y o f c o l o r pigmentation and p r o t e i n s o l u b i l i t y . A c c e l e r a t i o n o f Fermentation Musts

and F i n i n g

i n Late-Harvest

Despite t h e l a c k of wide market appeal, v i n t n e r s respond t o t h e connoisseur niche by o f f e r i n g an i n c r e a s i n g number of l a t e - h a r v e s t wines i n U.S. markets. Some of these wines are made from grapes having n a t u r a l l y r a i s i n i z e d by excessive sun exposure i n t h e vineyard. Sluggish fermentation r a t e s i n higher B r i x musts r e s u l t i n g from l a t e - h a r v e s t grapes can be a t t r i b u t e d t o an i n c r e a s e i n water a c t i v i t y - an osmotic f o r c e t a k i n g up water which places a dehydration strain called z v t o r r h y s i s on yeast c e l l s . An i n c r e a s e from 20 t o 50° Brix can reduce yeast cell volume by about 50%. M i n i m i z i n g B r i x l e v e l s , and t h e r e f o r e reducing t h e impact of t h i s phenomenon, has brought c l o s e r v i n t n e r s c r u t i n y upon i d e n t i f y i n g a r a t h e r p r e c i s e amount o f ethanol, r e s i d u a l sweetness, and a c i d balance d e s i r e d t o meet p e r c e i v e d consumer demand. Amidst c o o l e r temperatures and higher humidity Botrytis cinerea, the 'noble mold , can appear as fuzzy gray spots on grape s k i n s during t h e harvest season. B o t r y t i s spores bore through the s k i n s and e f f e c t an evaporation of berry water - i n t e n s i f y i n g r e t a i n e d sugars, a c i d i t y , g l y c e r o l , and f l a v o r s . The i n f e c t i o n process a c t u a l l y reduces sugar and a c i d i t y (increases g l y c e r o l and mucic acid) , but the net e f f e c t i s a c o n c e n t r a t i o n . B o t r y t i z e d f r u i t f l a v o r s undergo change due t o t h e formation of e t h y l e s t e r s of hydroxy-, keto-, and d i c a r b o x y l i c a c i d s . Yeast enzyme s y n t h e s i s and a c t i v i t y r a t e s determine how these a c i d s are metabolized i n t o t h e ultimate ester flavor p r o f i l e . Some n a t u r a l f r u i t f l a v o r s , such as the aromatic monoterpenes, g e r a n i o l and linalool, common to the Johannisberg Riesling, Gewurztraminer and Muscat v a r i e t i e s , a r e destroyed by b o t r y t i z a t i o n (15). 1



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The mold can a l s o form l a c c a s e , an enzyme capable of o x i d i z i n g important phenols, i n c l u d i n g anthocyanins. T h i s accounts f o r the golden-brown c o l o r s i n most b o t r y t i z e d wines. B o t r y t i s i n f e c t i o n can be q u a n t i f i e d u s i n g a l a c c a s e assay a v a i l a b l e i n l a b o r a t o r y k i t s . Samples are initially t r e a t e d with PVPP to reduce polyphenol i n t e r f e r e n c e and then mixed i n a spectrophotometer cell with a s y r i n g a l d a z i n e - e t h a n o l s o l u t i o n , along with a b u f f e r . The change i n absorbance i s recorded over s e v e r a l minutes and c a l c u l a t e d by formula t o provide l a c c a s e a c t i v i t y measured i n laccase u n i t s per mL. The b o t r y t i s fungus can reduce up t o h a l f of the p r o t e i n , amino a c i d , and f r e e ammonium n i t r o g e n (FAN) c o n s t i t u e n c y of grapes. Constrained FAN can induce deamination a c t i v i t y by yeasts upon p r o t e i n and amino a c i d c o n s t i t u e n t s - causing the development of unpleasant hydrocarbon f l a v o r s and other maladies of f l a v o r . FAN i s a more e s s e n t i a l element i n a c t i v e yeast growth and d e f i c i e n c i e s can be supplemented with diammonium phosphate and other food-grade sources. A more s e r i o u s problem i s a r e d u c t i o n of thiamine and other Β complexes necessary f o r d e c a r b o x y l a t i o n i n the p y r u v i c a c i d c y c l e and the s y n t h e s i s of v a r i o u s keto a c i d s mentioned above. These vitamins can a l s o be supplemented - o f t e n as components i n concert with FAN i n commercial p r o p r i e t a r y mixtures such as Yeastex . Yet another concern i s e x i s t i n g evidence i n d i c a t i n g b o t r y t i s a c t i v i t y can produce t r a c e amounts of a n t i b i o t i c s t h a t may be t o x i c t o yeasts (15) . B o t r y t i s i n f e c t i o n produces polygalacturonase which hydrolyses p e c t i n s i n t o p o l y s a c c h a r i d e s . Mucic a c i d development can r e a c t with calcium to form slow-developing precipitates. Both are hurdles to e f f e c t i v e f i n i n g evidenced by frequent observation of hazy wines i n the b o t t l e . Proper use of glucose oxidase enzymes f o l l o w e d by a p p r o p r i a t e a p p l i c a t i o n s of k i e s e l s o l f i n i n g mentioned below can provide a d d i t i o n a l help i n overcoming problem clarifications. Moderation of these p e r i l s and p i t f a l l s remains best c o n t r o l l e d by c l o s e monitoring of b o t r y t i s development i n the v i n e y a r d and blending techniques i n the c e l l a r . R

C o n t r o l of N a t u r a l Microorganisms I t remains r a t h e r commonplace f o r v i n t n e r s t o add 30-90 mg/L of f r e e s u l f u r d i o x i d e to grapes i n the crusher, or e a r l y on i n the r e s u l t i n g must. The t r a d i t i o n a l r a t i o n a l e f o r s u l f i t e a d d i t i o n s at the crush i s t h a t t h i s dosage i n h i b i t s or k i l l s w i l d y e a s t s , with a more secondary c o n t r o l of b a c t e r i a and molds, as w e l l as some p r o t e c t i o n from o x i d a t i o n . Research f i n d i n g s from Panagiotakopoulou and M o r r i s (6) i n d i c a t e s t h a t SO^ a d d i t i o n s a t the crusher a c t u a l l y i n c r e a s e browning i n r e s u l t i n g white wines. T r a d i t i o n a l


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problems with t h i s technique are t h a t high pH grape musts reduce molecular S0 and, t h e r e f o r e , i t s e f f e c t i v e n e s s ; poor and/or extended storage c o n d i t i o n s of potassium metab i s u l f i t e and other S0 sources reduce i o n a v a i l a b i l i t y ; deficient dosage calculations leaving the must unprotected; as w e l l as excessive dosage c a l c u l a t i o n s i n h i b i t i n g c u l t u r e d yeast and b a c t e r i a i n o c u l a t i o n s . While ' k i l l e r yeasts are not new t o enology, t h e i r r o l e i n reducing or e l i m i n a t i n g S0 a t the crusher i s an a p p l i c a t i o n t h a t i s r e l a t i v e l y r e c e n t . K i l l e r yeasts a r e species (the o r i g i n a l isolates were Saccharomyces cerevisiae) t h a t k i l l s e n s i t i v e members o f t h e i r own s p e c i e s and f r e q u e n t l y those of other s p e c i e s , as w e l l . They f u n c t i o n by s e c r e t i n g a plasmid-coded p r o t e i n t o x i n t h a t binds with 1,6 beta D-glucan r e c e p t o r components i n the c e l l w a l l s of s e n s i t i v e s t r a i n s . T h i s t o x i n i n t e r a c t s d i r e c t l y with p r o t e i n components of the c e l l membrane and, i n t u r n , d i s r u p t s the normal s t a t e of c e l l a c t i v i t y . Boone e t a l . (1) suggest t h a t k i l l e r yeasts a r e immune due to a p r e c u r s o r p r o t e i n t h a t f u n c t i o n s as an i n h i b i t o r o f t o x i n i n i t s c e l l membrane metabolic processes. K i l l e r yeasts are p a r t i c u l a r l y e f f e c t i v e i n reducing i n f e c t i o n from Brettanomyces. T h i s s p o i l a g e microorganism i s most o f t e n i d e n t i f i e d with r e d wine s p o i l a g e i n t h e form o f a c e t i c , i s o b u t y r i c and i s o v a l e r i c a c i d s which emerge as pungent, 'mousey' or 'horsey' odors. Brettanomyces can r e s i s t mid-range dosages o f f r e e S0 , i s i n s e n s i t i v e t o s o r b i c a c i d , and may go unnoticed u n t i l growth has become widespread. Consequently, musts undosed with S0 r e q u i r e immediate i n o c u l a t i o n with k i l l e r yeast c u l t u r e s i n order t o achieve maximal p r o t e c t i o n . Some e n o l o g i s t s i n o c u l a t e a t the crusher hopper - t a k i n g advantage o f heavy oxygen demand by the y e a s t s t o lower the o x i d a t i o n p o t e n t i a l . Van Vuuren and Jacobs (10) r e p o r t t h a t the k i l l e r system occurs i n some n a t u r a l yeast s t r a i n s . Musts i n o c u l a t e d with a s e n s i t i v e yeast s t r a i n c u l t u r e can be dominated by w i l d k i l l e r s t r a i n populations, causing stuck fermentations. These researchers p o i n t out t h a t t h e r e s u l t i n g wine can s u f f e r from reduced ethanol y i e l d , h i g h v o l a t i l e a c i d i t y , formation of H^S and contaminant f l a v o r s caused by acetaldehyde, f u s e l o i l s , and l a c t i c a c i d . V i n t n e r s continue t o evaluate a growing a v a i l a b i l i t y of k i l l e r yeast s t r a i n s . Popular s t r a i n s of k i l l e r y e a s t s are Champagne 111 and Montr ache t 1107. the l a t t e r more p o p u l a r l y known as 'Prisse de Mousse'. These and other s t r a i n s of c u l t u r e d k i l l e r yeasts are f r e q u e n t l y used by p r o g r e s s i v e winemakers. 2

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C o n t r o l o f Oxidation Sims e t a l . (9) r e p o r t that, while n o n - s u l f i t e d musts c o n t a i n high l e v e l s of polyphenoloxidase and r e s u l t a n t pigmentation o x i d a t i o n , the delay of s u l f i t i n g u l t i m a t e l y r e s u l t s i n wines of reduced t o t a l p h e n o l i c s and improved


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sensory quality. Panagiotakopoulou and Morris (6) conclude t h a t appropriate a d d i t i o n s of a s c o r b i c a c i d can a i d i n minimizing p e r s i s t e n t browning due t o o x i d a t i o n . Free oxygen i s rapidly utilized by cultured Saccharomyces spp. wine yeasts ( f a c u l t a t i v e anaerobes) a t the o u t s e t of l o g a r i t h m i c growth - with f u l l d e p l e t i o n of 0 r e s u l t i n g i n anaerobic fermentation. This condition r e s u l t s i n the r e d i s t r i b u t i o n of c e r t a i n l i p i d and s t e r o l compounds e s s e n t i a l f o r yeast membrane c o n s t r u c t i o n d u r i n g cell division - and membrane mechanics d u r i n g the g l y c o l y t i c f u n c t i o n s of fermentation. Some winemakers actually supplement oxygen by a g i t a t i n g white wine fermentations when a c t i v i t y commences t o d i m i n i s h - more o f t e n i n combination with FAN supplements, as w e l l . Oxygen present during the post-fermentation p r o c e s s i n g of young white wines r e q u i r e s an e n t i r e l y d i f f e r e n t approach. The g r e a t e r a wine's b u f f e r i n g c a p a c i t y , or i t s content of o x i d i z a b l e compounds, the g r e a t e r i t s aging p o t e n t i a l . Aging i s thus a c o n t r o l l e d process of o x i d a t i o n . Consequently, wines c o n t a i n i n g higher l e v e l s of yeast a u t o l y s i s compounds (wine fermented sur l i e s , or t r e a t e d with s i g n i f i c a n t a d d i t i o n s of yeast h u l l s ) and/or c o n t a i n i n g a b i t of f r e e S0 , are c h e m i c a l l y equipped t o bind with g r e a t e r q u a n t i t i e s of oxygen. The r e s u l t i s o f t e n measured i n wines having l e s s browning, w i t h more complexity and s t r u c t u r e i n the f l a v o r p r o f i l e . Higher l e v e l s of phenols, as found i n longer-term s k i n c o n t a c t musts, a l s o i n f l u e n c e a higher b u f f e r i n g c a p a c i t y , and account f o r the major reason why red wines, p a r t i c u l a r l y a t lower pH l e v e l s , g e n e r a l l y take f a r longer p e r i o d s of time i n aging t o maturity. While oxygen can be employed e f f e c t i v e l y i n making complex white t a b l e wines, those designed t o be l i g h t e r i n s t y l e , more f r e s h and f r u i t y i n aroma, should be made from g e n e r a l l y lower pH grapes a f f o r d e d minimized oxygen exposure. S u l f i t i n g at the crusher may continue t o be a d v i s a b l e as r e s u l t i n g increases i n phenols are o f t e n balanced with r e s i d u a l sweetness i n these types of wine. Cold temperature short term aging i n s t a i n l e s s s t e e l tankage, n i t r o g e n sparging, and adequate maintenance of f r e e S0 l e v e l s are e s s e n t i a l f o r optimal q u a l i t y i n these wines.


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Red Wine C o l o r Enhancement and

Stability

Some red grape v a r i e t i e s , such as Pinot N o i r , are o f t e n c o l o r d e f i c i e n t - c e r t a i n l y i n comparison t o the dense pigmentation g e n e r a l l y found i n wines made from Cabernet Sauvignon and P e t i t e S i r a h . While some wine a f i c i o n a d o s accept delicate color values as p a r t of varietal c h a r a c t e r , indeed, darker Pinots are h e l d suspect by wine judges, some question remains whether or not the o v e r a l l image of red wines i s n e g a t i v e l y i n f l u e n c e d by modest hue intensities. Sugar r e s i d u e s i n the formation of anthocyanin types,



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i . e . , monoglucosides and d i g l u c o s i d e s , p l a y a dramatic r o l e i n wine c o l o r s t a b i l i t y , as do the types of anthocyanins themselves. Monoglucoside forms of malvadin and p e o n i d i n are dominant i n most commercially-grown red v a r i e t i e s of Vitis vinifera. D i g l u c o s i d e forms of d e l p h i n i d i n and p e t u n i d i n , found i n Vitis labrusca and other s p e c i e s , are the l e a s t s t a b l e . Hybrid c u l t i v a r s , as would be expected, e x h i b i t a wide range of c o l o r hue, i n t e n s i t y , and s t a b i l i t y i n r e l a t i o n s h i p t o p a r e n t a l genetic influence. Optimal c o l o r s t a b i l i t y can be achieved by c l o s e l y monitoring pH during the h a r v e s t season. Lower pH, i n the 3.20-3.30 range, i s g e n e r a l l y a s s o c i a t e d with r i c h e r , more p u r p l i s h tones, while higher pH ranges are u s u a l l y expressed i n b r i c k - r u b y hues. V i n t n e r s o f t e n choose to enhance c o l o r by s e p a r a t i n g f r e e - r u n or l i g h t l y pressed j u i c e f o r pink • b l u s h wines or 'blanc de n o i r s ' t a b l e and s p a r k l i n g wine cuvees. The remaining pomace i s then added t o other crushed grapes t o i n c r e a s e the a v a i l a b i l i t y f o r increased pigment e x t r a c t i o n when fermented i n t r a d i t i o n a l s k i n c o n t a c t methods. E x a c t i n g c o n t r o l over the extent of e x t r a c t i o n i s necessary i n order to avoid generating d i s t o r t e d f l a v o r p r o f i l e s and saturated concentrations of p h e n o l i c s - as w e l l as excessive astringency, b i t t e r n e s s , and eventual color precipitates. A more simple method i s by simple b l e n d i n g of a ' t e i n t u r i e r ' , a dense, inky wine made from Salvador, C o l o b e l , and other h e a v i l y pigmented grape v a r i e t i e s . Sometimes heavily-pigmented press wine f r a c t i o n s are employed i n a s i m i l a r manner. V i n t n e r s d i f f e r i n t h e i r approach t o t h i s as some f e e l the blend s t r a y s from the i d e a l s of v a r i e t a l p u r i t y , while others p o i n t out t h a t many c l a s s i c reds, such as Bordeaux, are blends among d i f f e r e n t v a r i e t i e s anyway. New products made p o s s i b l e by membrane s e p a r a t i o n p r o c e s s i n g techniques explained below have r e s u l t e d i n the i s o l a t i o n of concentrated pigments i n r e t e n t a t e form. While t h i s may c a r r y s i m i l a r concerns of v a r i e t a l p u r i t y , i t does so on a f a r smaller s c a l e as comparatively l i t t l e pigment i s r e q u i r e d to achieve f a v o r a b l e r e s u l t s . A product c a l l e d X p r e s s i s now a v a i l a b l e i n s e v e r a l forms designed to f i t the most common needs in color enhancement. 1

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Reduction of Astringency and B i t t e r n e s s The e x t r a c t i o n of complex polyphenols from grape seeds, s k i n s , and stems, has been a problem of v a r y i n g magnitude. Commercial white wines g e n e r a l l y have only minor c o n s t i t u e n c i e s of phenols due to the e x t r a c t i o n of j u i c e p r i o r t o fermentation. On the other hand, e x c e s s i v e treatments i n the crusher and press ( g e n e r a l l y t o maximize j u i c e y i e l d ) c r e a t e the r i s k of cracked seeds, macerated s k i n s and stem fragments c o n t r i b u t i n g s i g n i f i c a n t l y t o a s t r i n g e n c y and b i t t e r n e s s i n the f i n i s h e d wine. In red



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wines the conventional v i n i f i c a t i o n method i s t o ferment the must i n t o t a l contact with grape s o l i d s i n order t o r e l e a s e anthocyanin c o l o r pigments from the s k i n s - a process ranging from s e v e r a l days up t o s e v e r a l months. T h i s technique aggravates e x t r a c t i o n of a s t r i n g e n t and b i t t e r phenols - c o n d i t i o n s o f t e n r e f e r r e d t o as •tannic' and 'harsh' i n wine jargon. Most e n o l o g i s t s c a t e g o r i z e phenols i n t o two major groups. Polymeric f l a v o n o i d s comprise the largest f r a c t i o n of p h e n o l i c compounds i n wines and can be t r a c e d t o the p r o c e s s i n g described above, as w e l l as from degradation of l a r g e r molecular components. Flavonoids serve as oxygen r e s e r v o i r s which c o n t r i b u t e t o o x i d a t i o n r e a c t i o n s important i n wine aging and development. Nonf l a v o n o i d s comprise a much smaller p o r t i o n of phenol c o n s t i t u e n c y i n wines and are g e n e r a l l y more aromatic, p a r t i c u l a r l y the aldehyde compounds r e s u l t i n g from wood aging regimens. With t h i s d i v e r s i t y i n a t t r i b u t e s , c l o s e a t t e n t i o n t o the management of o v e r a l l p h e n o l i c p r o f i l e i n wines i s an e s s e n t i a l element i n wine q u a l i t y . Up u n t i l r e l a t i v e l y r e c e n t l y , grape crusher-stemming machines have been a major source of e x c e s s i v e phenols. Some o l d e r devices served t o m i l l the grapes i n t o small p a r t i c l e s of s o l i d s c r e a t i n g an immense s u r f a c e area f o r extraction. L a t e r models were equipped with a d j u s t a b l e r o l l e r s i n order t o reduce maceration. Contemporary u n i t s such as the AMOS are a v a i l a b l e t h a t separate grape b e r r i e s from the stem r a c h i s without crushing. Some winemakers have removed crusher r o l l e r s a l t o g e t h e r and dump t h e i r grapes d i r e c t l y into the c o n v e n t i o n a l destemming chamber. Stem t a n n i n e x t r a c t i o n can then be more p r e c i s e l y monitored by adding back a d e s i r e d percentage of stems, i f any, t o the must. The a p p l i c a t i o n of these p r i n c i p l e s have had a very p o s i t i v e impact upon reducing wine astringency and b i t t e r n e s s . S i m i l a r h i s t o r y has evolved i n press equipment. E a r l y mechanization f o r r o t a t i n g the press basket served t o i n c r e a s e j u i c e y i e l d s by the movement of must p a s s i n g a g a i n s t the screen w a l l s . These dynamics a l s o i n c r e a s e d commensurately more p h e n o l i c s . The p r e s s i n g of red wines a f t e r must fermentation i s p a r t i c u l a r l y s e n s i t i v e t o phenol e x t r a c t i o n - with most winemakers i n s i s t i n g upon the s e p a r a t i o n of 'free run' and 'press' wines. Later e v a l u a t i o n of the press wine determines i t s percentage i n the assemblage of the f i n a l wine blend (13). R

The tank press i s comparatively new t o commercial winemaking, and b e t t e r methods of a p p l i c a t i o n have continued e f f i c i e n c y i n y i e l d s while markedly lowering phenolic extraction. The device c o n s i s t s of a c l o s e d s t a i n l e s s s t e e l h o r i z o n t a l tank i n which a membrane i s constructed so as to d i v i d e the interior in half lengthwise. The membrane separates the tank i n t o a press chamber and a pneumatic chamber. I n f l a t i o n of the l a t t e r e x e r t s a f i r m but gentle and even pressure upon the must



8. VINE


139

on the opposite s i d e of the membrane. There are no b a f f l e s , chains, r i n g s , or other devices employed t o loosen the must/pomace cake - a major source of maceration i n the o l d e r r o t a t i n g basket presses. Tank presses o f f e r the d i s t i n c t advantage of r e s i s t i n g pomace cake formation due t o the e l a s t i c i t y of the membrane. Figure 1 i l l u s t r a t e s the l i q u i d e x t r a c t i o n process due t o the slowly moving must against the channel o u t l e t pores s i t u a t e d upon the inner press chamber. T h i s c r e a t e s a f a r more g e n t l e agitation as the tank r o t a t e s and s i g n i f i c a n t l y reduces phenolic c o n c e n t r a t i o n s . Some winemakers have achieved red wine q u a l i t y so high t h a t they no longer have the need t o separate f r e e and press wine f r a c t i o n s (13). Enrichment of D i a c e t y l Components The d e s i r e f o r r i c h e r , l e s s f r u i t y and more complex r e d and white t a b l e wines has l e d t o a growing body of r e s e a r c h and a p p l i e d techniques a s s o c i a t e d with i n c r e a s i n g the d i a c e t y l , or ' b u t t e r y , c h a r a c t e r . T h i s i s achieved by one major pathway - m a l o - l a c t i c (ML) bacterial fermentation, g e n e r a l l y i n i t i a t e d by c u l t u r e i n o c u l a t i o n s i n young wines. The r e a c t i o n i s a c a t a b o l i c pathway i n which L-malic a c i d i s enzymatically o x i d i z e d t o L - l a c t i c a c i d , carbon d i o x i d e gas, and energy. Total titratable a c i d i t y i s s i g n i f i c a n t l y reduced and pH i n c r e a s e d i n the process. By-products from the conversion i n c l u d e a c e t o i n and 2,3-butanediol, acetic acid, and the diacetyl component of p r i n c i p a l i n t e r e s t . Most c u l t u r e d l a c t i c a c i d b a c t e r i a are found i n the species, Leuconostoc oenos and Lactobacillus spp., e x i s t i n g as f a c u l t a t i v e anaerobes. T h i s may be b o r d e r l i n e as some s t u d i e s i n d i c a t e t h a t higher 0 c o n c e n t r a t i o n s can i n h i b i t ML fermentation - and other e q u a l l y sound r e s e a r c h i n d i c a t e s q u i t e the opposite. While the c o r r e l a t i o n of f r e e oxygen a n a l y s i s can r e v e a l h i s t o r i c a l p a t t e r n s f o r ML behavior, there i s no f i n i t e s e t of p r e d i c t o r s . Such i s the f a s t i d i o u s nature of these microorganisms. More d e f i n i t i v e wine b a c t e r i a c h a r a c t e r i s t i c s are provided i n Table 1. More c o n s i s t e n t i s the importance of lower S0 l e v e l s , moderate temperature, and higher pH range r e q u i r e d f o r ML fermentation. Free S0 l e v e l s g r e a t e r than 20 mg/L can be expected t o slow or stop a c t i v i t y of the b a c t e r i a . A r a t h e r narrow window of temperature, 20-25°C i s g e n e r a l l y considered i d e a l . The popular PSU-1 c u l t u r e t o l e r a t e s comparatively lower pH l e v e l s - i n the 3.20-3.40 range, while the e q u a l l y accepted ML-34 s t r a i n i s more adaptable i n ranges higher than 3.40. Cultured ML organisms are h e t e r o t r o p h i c and t h e r e f o r e unable t o synthesize important n u t r i e n t s from most n a t u r a l l y - o c c u r r i n g sources. Consequently, young wines t y p i c a l l y r e q u i r e a d d i t i o n s of Β complex v i t a m i n s - o f t e n i n the form of yeast cytoplasm e x t r a c t s r e f i n e d from 1

2

2

2



F i g u r e 1. Operation of a T y p i c a l Tank Press Adapted from: Food Technology I n t e r n a t i o n a l Europe (13)


8. VINE

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a u t o l y s a t e s . I t i s from t h i s r a t i o n a l e t h a t an i n c r e a s i n g number of v i n t n e r s leave young wines 'sur l i e s , o r on fermentation sediment r i c h i n dead yeast c e l l s . Some winemakers a c t u a l l y i n o c u l a t e wines with ML b a c t e r i a l d u r i n g primary yeast fermentation i n order t o take maximum advantage of higher yeast populations and t h e r e f o r e g r e a t e r a v a i l a b l e a u t o l y s a t e s u b s t r a t e s . Opinions d i f f e r i n support of t h i s as some evidence e x i s t s i n d i c a t i n g a c t i v e yeast growth may r e t a r d ML b a c t e r i a l development. Proper development of d i a c e t y l and r e l a t e d complexity components r e q u i r e wine exposures open t o the hazards o f v a r i o u s other types of i n f e c t i o n and malady. A very sound program o f assurance i s needed. Simple paper chromatograms can s u f f i c e i n monitoring t h e m a l i c - l a c t i c conversion, but e a r l y i n d i c a t o r s of a c e t i c a c i d - e t h y l acetate v o l a t i l e acidity from Acetobacter spp. a r e essential. D i a c e t y l can be q u a n t i f i e d by a d i s t i l l a t i o n and spectrophotometric procedure provided by Z o e c k l e i n (15). V o l a t i l e a c i d i t y i s adequately and e a s i l y measured by t h e t r a d i t i o n a l Cash d i s t i l l a t i o n procedure (11).


1

Identification Mercaptans

and

Control

of

Hydrogen

Sulfide

and

The development of only t r a c e q u a n t i t i e s o f hydrogen s u l f i d e and mercaptans i n wine r e s u l t s i n f o u l odors which can s e r i o u s l y d e t r a c t from wine q u a l i t y and v a l u e . Elemental s u l f u r , o f t e n t r a c e d t o vineyard spray r e s i d u e s , i s t h e p r i n c i p a l precursor. With continued r e d u c t i o n of l a b e l s a u t h o r i z e d f o r v i t i c u l t u r a l use, r e l i a n c e upon s u l f u r compounds i n the vineyard has grown. This i n c r e a s e d usage has given r i s e t o a commensurate advance i n t h e magnitude of problems a s s o c i a t e d with elemental sulfur. Winemakers encourage maximum time intervals, t y p i c a l l y not l e s s than a month, between s u l f u r treatments i n the f i e l d and grape harvest. A p p l i c a t i o n s o f c o l l o i d a l s u l f u r g e n e r a l l y r e s u l t i n heavier elemental sulfur r e s i d u e s , although the dusting, p r e c i p i t a t e d , and wettable forms are major sources, too. P r o g r e s s i v e winegrowers a r e now a p p l y i n g micronized s u l f u r ( p a r t i c l e s which a r e l e s s than 10 urn) d i s s o l v e d i n water. Another source of elemental s u l f u r i s the residue from burning s u l f u r s t i c k s i n s i d e wooden aging and storage v e s s e l s . A l t e r n a t i v e methods of d i s i n f e c t i n g , such as t h e use o f l i v e steam o r potassium m e t a - b i s u l f i t e f o r s h o r t e r term, and the burning of d r i p l e s s s u l f u r devices f o r longer term, are now widely employed. According t o Eschenbruch (4) , t h e normal growth pathway of wine yeasts r e q u i r e s about 5 mg/L of s u l f a t e f o r r e d u c t i o n t o elemental s u l f u r i n c e l l metabolism from grape musts t h a t c o n t a i n up t o 700 mg/L o f a v a i l a b l e sulfate. The s y n t h e s i s of hydrogen s u l f i d e from t h i s r e d u c t i o n i s , thus, inherent with fermentation. F i g u r e 2 p o r t r a y s the formation of H S and mercaptans by y e a s t s . 2


142


Table 1. P h y s i o l o g i c a l C h a r a c t e r i s t i c s o f Wine B a c t e r i a Gram reaction

Organism


Gluconobacter Acetobacter Lactobacillus Leuconostoc Pediococcus Bacillus

Catalase

+ +/-

neg. ncg. pos. pos. pos. pos.

Adapted from:

--

+

Oxygen reqs.

Major endprd.

Aer. Aer. Aer./ana. Fac./ana. Aer./ana. Aer.

Acetic Acetic Lactic Lactic Lactic Several

Sporulation neg. neg. neg. neg. neg. pos.

P r o d u c t i o n Wine A n a l y s i s 1990 (15) SULFATE (SO;") ^

(1)

ATP k

Pyrophosphate (PPj)

ADENOSINE-S'-PHOSPHOSULFATE (APS)

f

ATP

a) ADP 3* PHOSPHATE-5'-PHOSPHOSULFATE s>

(PAPS)

2c + 211 +

(3)

2

SULFITE (S0 * ) + ADENOSINES.S'-BIPHOSPIIATE 3

s 6e%6!I*

(4) ^111 π 2

SULFIDE (S *)

Γ

CYSTEINE

METHIONINE

+2H +

1 H S 2

MERCAPTANS Pyruvate • NH

3

ILS MERCAPTANS

F i g u r e 2. Formation of Hydrogen S u l f i d e and Mercaptans by Yeasts Adapted from: Production Wine A n a l y s i s 1990 (15)


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Optimal removal of suspended grape s k i n fragments, pulp and other s o l i d s i n white j u i c e p r i o r t o fermentation commensurately reduces one of the h i g h e s t sources o f elemental s u l f u r . Wild yeasts and tumultuous fermenting y e a s t s a r e a s s o c i a t e d with greater l e v e l s o f d e t e c t a b l e H S ' r o t t e n egg' odor. Epernay 2 and P r i s e de Mousse y e a s t s s y n t h e s i z e l e s s e r degrees of H S, while t h e Montrachet and Steinberg s t r a i n s g e n e r a l l y r e s u l t i n comparatively higher l e v e l s . Deficiencies i n essential v i t a m i n s , as w e l l as FAN, are a s s o c i a t e d with i n c r e a s e d p r o d u c t i o n of H S due t o the s t i m u l a t i o n of p r o t e o l y t i c deamination r e a c t i o n s t r i g g e r e d by s t r e s s e d y e a s t s . Mercaptans a l s o r e s u l t from elemental s u l f u r and, even a t t r a c e l e v e l s , are s i g n i f i c a n t l y more pungent than H S. The t y p i c a l sensory response t o mercaptans i s a 'skunky' odor, although i t i s the methyl and e t h y l mercaptan forms t h a t are found i n wine, while skunk spray i s comprised of the η-butyl mercaptan form. Methyl mercaptan, the most common wine malady, i s formed from t h e amino a c i d methionine - t y p i c a l l y as r e s u l t o f yeast deamination due t o f r e e ammonium n i t r o g e n d e f i c i e n c y stress. E t h y l mercaptan i s formed by t h e presence o f acetaldehyde c a t a l y z e d by H S t o form the intermediate thioacetaldehyde and water (15). Contemporary winemakers use the assurance of adequate e s s e n t i a l vitamins and FAN a v a i l a b i l i t y i n fermenting musts as the most e f f e c t i v e safeguard a g a i n s t the formation of H S and mercaptans. While the a n a l y s i s of these c o n s t i t u e n t s provide a d i f f i c u l t h u r d l e f o r most commercial e n o l o g i s t s , reasonably good c o r r e l a t i o n s can be made by u s i n g i o n s e l e c t i v e e l e c t r o d e s with expanded-scale pH/mV meters f o r the determination of ammonia. E a r l y on d e t e c t i o n i s another key p a r t of c o n t r o l . Z o e c k l e i n e t a l . (15) have devised a method of s e p a r a t i n g H S and mercaptans with copper s u l f a t e and cadmium s u l f a t e reagents i n the l a b o r a t o r y t o f a c i l i t a t e b e t t e r sensory determination more quickly and easily. Cooler fermentation temperatures are conducive t o lower HS formation and can allow f o r b e t t e r sensory d e t e c t i o n e a r l y on i n fermentation - o f f e r i n g the p o s s i b i l i t y f o r a e r a t i o n or C0 t o help sparge H S. A e r a t i o n during r a c k i n g can a l s o help t o v o l a t i l i z e H S, but a t the r i s k o f o x i d a t i o n and browning - l e s s a concern f o r reds than whites. Bentonite f i n i n g can reduce H S, but does not g e n e r a l l y e f f e c t a complete removal. Sulfur dioxide a d d i t i o n s can a l s o reduce H S by o x i d i z i n g i t back t o elemental s u l f u r . The most e f f e c t i v e and commonly used treatments are with appropriate p r e s c r i p t i o n s of copper s u l f a t e - which can reduce or remove both H S and mercaptans. 2

2


2

2

2

2

2

2

2

2

2

2

2

2

B e t t e r A p p l i c a t i o n s of F i n i n g s Despite t h e improved stemmers and presses,

mechanical v i r t u e s of c r u s h e r some r e d grape v a r i e t i e s under



144


unusual growing c o n d i t i o n s can s t i l l be p r o b l e m a t i c a l i n r e l e a s i n g p h e n o l i c compounds and suspended s o l i d s . One of the most p e r s i s t e n t problems i n white wine f i n i n g i s the determination of s o l u b l e p r o t e i n content. Far g r e a t e r l e v e l s of e x t r a c t e d phenols e l i m i n a t e s a concern f o r p r o t e i n i n s t a b i l i t y i n red wines. The use of f i n i n g s , or c l a r i f i c a t i o n agents, goes back s e v e r a l c e n t u r i e s - although much of the technology i n understanding t h e i r use i s new. One traditional problem has been the excessive use of finings, p a r t i c u l a r l y bentonite, c a s e i n , and g e l a t i n , a l l of which can s e v e r e l y reduce c o l o r and f l a v o r . On the other hand, deficiencies i n prescribing finings can result in suspended s o l i d s remaining which can be s u b s t r a t e s f o r eventual enzymatic degradation of wine. These can r e s u l t i n an unpleasant 'mousey a f t e r t a s t e y e t remaining f o r research to precisely identify. U n d e r f i n i n g can a l s o allow copper and i r o n t o remain i n i o n i c form and cause l a t e r haziness or 'casse' (12). Brenna and DeVecchi (2) have r e p o r t e d the development of a new assay f o r the determination of s o l u b l e p r o t e i n s i n order t o v e r i f y e f f e c t i v e n e s s of f i n i n g i n white wines. Wine samples are g e l f i l t e r e d i n mini-columns packed with Sephadex* i n a t a r t r a t e - e t h a n o l s o l u t i o n . Phenols are bound by a dye on the column and t h u s l y e l i m i n a t e d from interference. The a n a l y s i s i s s i m p l i s t i c and low c o s t , t a k i n g about one h a l f hour t o perform - although m u l t i p l e columns can be e a s i l y employed t o render a s e r i e s of assays i n d i v i d u a l l y more time e f f i c i e n t . Some v i n t n e r s have returned t o a more t r a d i t i o n a l approach employed i n Europe - t h a t of 2 t o 4 egg whites beaten t o a f r o t h and then added t o each 100 g a l l o n s or so of wine i n b a r r e l . Adding a l i g h t dose of t a n n i c a c i d beforehand helps t o prevent the formation of degradation compounds from p h e n o l i c s i n the wine. The egg white r e a c t i o n with the t a n n i c a c i d forms a f i n e g r a n u l a r suspension t h a t a t t r a c t s suspended p a r t i c l e s t h a t become a mass heavy enough t o p r e c i p i t a t e . While t h i s i s a r a t h e r f a s c i n a t i n g operation t o witness i n romantic o l d wine c e l l a r s , i t i s a t best d i f f i c u l t t o manipulate and time i n t e n s i v e (12). One of the newest f i n i n g agents i s c o l l o i d a l s i l i c a perhaps b e t t e r known as ' k i e s e l s o l ' . Use of t h i s compound r e q u i r e s a p r i o r treatment of p r o t e i n f i n i n g , such as c a s e i n , g e l a t i n , or egg white mentioned above, but a t a reduced r a t e . Various grades and types of k i e s e l s o l s have widely r e p l a c e d bentonite i n Europe and i n c r e a s i n g l y so i n the U.S. I t can be added d i r e c t l y t o the wine without the time-consuming s l u r r y preparations r e q u i r e d by b e n t o n i t e and q u i c k l y coagulates t o embrace any phenol degradation products t h a t may have r e s u l t e d from the p r o t e i n f i n i n g addition beforehand. The important advantages of k i e s e l s o l are i t s r e l u c t a n c e t o reduce c o l o r and f l a v o r u n l e s s they are already p r e c a r i o u s l y unstable - and a b r i l l i a n c y t h a t has encouraged an i n c r e a s i n g amount of b o t t l i n g without f i l t r a t i o n (12). 1


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145



Q u a l i t y Improvements by Membrane Separation

Techniques

Contemporary psychographic t a s t e s and preferences have r e s u l t e d i n an i n c r e a s i n g concern about the human d i e t and the amount of a l c o h o l consumed i n wine d r i n k i n g . Consumer demand f o r low and no a l c o h o l wines grows i n appeal t o commercial wine s u p p l i e r s and has generated an expanded i n t e r e s t i n membrane separation technology. As t h i s body of knowledge has grown, other uses of membrane s e p a r a t i o n have been employed f o r improving wine q u a l i t y . The p r i n c i p l e involves the s e p a r a t i o n of one l i q u i d into two of varying properties by virtue of a semipermeable b a r r i e r which c o n t r o l s the v e l o c i t y of v a r i o u s molecules between i t s two s i d e s . In s h o r t , i t s a molecular s i e v e . Depending upon the s p e c i f i c p r o p e r t i e s of t h i s s i e v e , membrane separation i s c l a s s i f i e d thus: •Microfiltration' (MF), 'Ultrafiltration (UF), and 'Reverse Osmosis' (RO). Retention ranges are provided i n Table 2 . Membrane separation u n i t s t y p i c a l l y c o n s i s t of a h o l d i n g v e s s e l from which untreated l i q u i d i s s t o r e d ; a pump t h a t feeds the l i q u i d a t a proper r a t e and v e l o c i t y ; and a module t h a t houses the membranes. T h i s type of system i s i l l u s t r a t e d i n Figure 3. J u i c e or wine i s a p p r o p r i a t e l y pressured upon the i n l e t t o the module and a permeate stream f r e e of s o l i d s r e t a i n e d by the membrane, passes through and i s c o l l e c t e d . The r e t e n t a t e i s the concentrated l i q u i d r e t a i n e d which flows over the membrane and i s c o l l e c t e d s e p a r a t e l y . The r a t e of flow is called the f l u x and is directly p r o p o r t i o n a l t o lower pump pressures (permeate f l u x a t higher pressures i s non-pressure dependent) and i n v e r s e l y p r o p o r t i o n a l t o membrane r e s i s t a n c e (13). MF d i s c r i m i n a t e s by p a r t i c l e s i z e and has been s u c c e s s f u l i n e l i m i n a t i n g the need f o r bentonite f i n i n g , as w e l l as c e n t r i f u g a t i o n and f i l t r a t i o n . This also provides the added advantages of conserving d e l i c a t e c o l o r and f l a v o r components, while a l s o being more c o s t e f f e c t than more conventional processes. Membranes gauged f o r lower molecular weight s o l u t e s can a l s o bar the passage of microorganisms - r e s u l t i n g i n s t e r i l e wine products and l e s s e r dosages of t r a d i t i o n a l wine p r e s e r v a t i v e s (14). UF separates on the b a s i s of chemical s t r u c t u r e s i n solution with ranges t y p i c a l l y designed for large molecular weights such as c o l l o i d s and polymers - f i n d i n g e x c e l l e n t a p p l i c a t i o n s i n reducing p r o t e i n i n s t a b i l i t y and s e p a r a t i o n of c o l o r pigments t h a t have browned due t o o x i d a t i o n (14). F l o r e s et a l . (5) s t u d i e d the e f f e c t s of UF on aroma and f l a v o r c h a r a c t e r i s t i c s of Johannisberg R i e s l i n g and Gewurztraminer wines. Laboratory and p l a n t t r i a l s g e n e r a l l y f a i l e d t o show a s i g n i f i c a n t l o s s of f r u i t aroma by extensive sensory e v a l u a t i o n s . RO membranes i n h i b i t the flow of comparatively lower 1


146


T a b l e 2.

Membrane R e t e n t i o n o f Wine Components


Relative Retention of Wine Components Membrane Separation Process

None

Partial

Total

RO

Water, ethanol, acetic acid, etc.

Acetaldehyde, glycerol, simple phenolic compounds, aromatic components, esters, etc.

Salts, glucose, tlavonotds, macromolecules, microorganisms, and suspended particulates.

All the soluble components with M W below 1000: amino acids, simple phenolic compounds, tlavonoid monomers, etc.

Oligomers of flavonoids, peptides and all components with MW between 1000 and 10000.

Compounds with MW greater than 10000: proteins, polysaccharides, •olymers of falvonoids, microorganisms and suspended particulates.

All compounds with MW below 100000. .All the soluble components.

Colloids with MW between 100000 and 10000000.

Colloids of MW greater than 1000000, microorganisms and suspended particles.

MF

Adapted from: Proceedings o f 7 t h I n t e r n a t i o n a l Conference i n Food S c i e n c e & Technology 1992 (14)

three way valve

concentrate storage tank

permeate

pump

F i g u r e 3. Membrane Separation System Adapted from: Proceedings of 7th I n t e r n a t i o n a l Conference i n Food Science & Technology 1992 (14)



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molecular weight s o l u t e s and serves t o concentrate j u i c e or wine t o products t h a t are heavier-bodied and r i c h e r i n c o l o r and f l a v o r . The RO a p p l i c a t i o n a l s o has t h e advantages of c o o l temperature o p e r a t i o n as opposed t o evaporator c o n c e n t r a t i o n and f a r l e s s demand f o r energy. T h i s can a l s o supersaturate i o n i c potassium and t a r t a r i c acid i n solution - aiding i n faster p r e c i p i t a t i o n of u n s t a b l e potassium b i t a r t r a t e c r y s t a l s . Deposits o f these a r g o l s f r e q u e n t l y form on equipment s u r f a c e s c a u s i n g r e s t r i c t e d product flow. E l e c t r o d i a l y s i s , c o n s i s t i n g o f e l e c t r o l y t e s m i g r a t i n g through an anion impermeable membrane on one s i d e and a c a t i o n impermeable membrane on the other, both under the e f f e c t o f an e l e c t r i c f i e l d , can minimize t h e presence of potassium i o n s . Electrodialysis can a l s o be e f f e c t i v e i n the r e d u c t i o n of acetaldehyde and s u l f u r o u s a c i d content i n wine (24). For a l c o h o l r e d u c t i o n o r removal, t h e system i s designed with a membrane s e l e c t i v e only f o r a l c o h o l permeate, while t h e remaining c o n s t i t u e n t s form t h e r e t e n t a t e . A l c o h o l c o n c e n t r a t i o n l e v e l s a r e c o n t r o l l e d by i n t r o d u c i n g a flow of water on t h e permeate s i d e o f t h e membrane - c a r r y i n g away a l c o h o l molecules and thus reducing t h e a l c o h o l c o n c e n t r a t i o n on t h e r e t e n t a t e (product) s i d e (14). F u l l y ripened grapes c u l t i v a t e d i n c o o l e r c l i m a t e s are o f t e n d e f i c i e n t i n d e s i r e d sugar content. S e n s i t i v i t y to this can be e x e m p l i f i e d by t h e German wine c l a s s i f i c a t i o n system which i s based upon sugar/ripeness parameters - as compared t o a geographical b a s i s i n most other European countries. The p r a c t i c e o f sugar a d d i t i o n s , o r C h a p t a l i z a t i o n . has long been c r i t i c i z e d as a breach of e t h i c s - and commercially p r o h i b i t e d i n C a l i f o r n i a . A recent study conducted Duitschaever e t a l . (3) concludes t h a t Johannisberg R i e s l i n g wines made by musts concentrated by RO were higher i n q u a l i t y than those which were C h a p t a l i z e d . Premature grapes s u f f e r i n g from an abbreviated growing season a r e , however, often e x c e s s i v e l y h i g h i n a c i d and phenol c o n s t i t u e n t s - a situation aggravated even f u r t h e r by c o n c e n t r a t i o n . Pompei (7) suggests t h a t these excesses can be r e l i e v e d by r e c t i f i c a t i o n p r i o r t o RO treatment, but t h e l a c k o f f l a v o r development i n green f r u i t o f t e n f a i l s t o j u s t i f y the c o s t o f such p r o c e s s i n g . B e t t e r Economies i n B o t t l i n g and Packaging With the i n c r e a s e d investment i n machinery and maintenance expense necessary t o "in-house" b o t t l e and package wine many v i n t n e r s have opted t o c o n t r a c t mobile s e r v i c e s t o perform t h i s f u n c t i o n (13). Apart from the cost aspects mentioned above, mobile b o t t l i n g a l s o permits b e t t e r e f f i c i e n c i e s o f both time and space. T h i s tends t o i n c r e a s e i n importance i n v e r s e l y with winery s i z e . The smaller t h e o p e r a t i o n , t h e l e s s time i s u s u a l l y devoted t o b o t t l i n g and packaging -

American Chemical Society Library In Beer and Wine Production; Gump, B., et al.; ACS Symposium Series; American Society: Washington, DC, 1993. 1155 Chemical 16th St. N. W.


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i n c r e a s i n g c o s t on a per u n i t output b a s i s . I t follows t h a t such equipment i s thus o v e r s i z e d - i n f l u e n c e d p r i m a r i l y by l i m i t e d s e l e c t i o n s i n down-sized model a v a i l a b i l i t i e s from manufacturers. The area r e p l a c e d by mobile b o t t l i n g i n most small w i n e r i e s ranges from 500 t o more than 1,000 square f e e t . In some of the more expensive v i n i c u l t u r a l r e a l e s t a t e l o c a l e s t h i s can exceed $100,000 of investment, with a s i m i l a r o u t l a y f o r the a c t u a l b o t t l i n g and packaging equipment. Opportunity c o s t f o r a modest 10,000-case winery can e a s i l y be double the c o s t of mobile b o t t l i n g . Setup, t r i a l and e r r o r , waste, as w e l l as t r a i n i n g and r e t r a i n i n g , are a l s o major c o s t j e o p a r d i e s inherent with small winery in-house b o t t l i n g and packaging operations. Custom b o t t l i n g firms quote p r i c e s f o r b o t t l i n g and packaging s e r v i c e s on s i t e at l e s s than $2 per case s i g n i f i c a n t l y l e s s i f only a f r o n t l a b e l i s a p p l i e d . In t h a t the mobile b o t t l i n g equipment i s r e g u l a r l y used, i t i s e f f e c t i v e l y maintained and, e q u a l l y important, r e p l a c e d with more p r o d u c t i v e and e f f i c i e n t u n i t s . The v i n t n e r thus b e n e f i t s from s t a t e - o f - t h e - a r t equipment and m a t e r i a l employed t o optimize wine q u a l i t y . Quantity d i s c o u n t s are i n v o l v e d with p r i c i n g , as are mileage and f i l t e r usage considerations. Experienced p r o f e s s i o n a l operators and guaranteed r e s u l t s are a d d i t i o n a l a t t r a c t i v e appeals i n f a v o r of the custom s e r v i c e . Scheduling can be p r o b l e m a t i c a l with mobile b o t t l i n g , although competition and advance planning continue t o reduce this disadvantage. Conscientious vintner p r e p a r a t i o n p r i o r t o mobile a r r i v a l i s c r i t i c a l as winery caused down time may be charged a t r a t e s of $150 per hour and more. Unfortunately, t h i s type of s e r v i c e remains l i m i t e d to o n l y the more concentrated winegrowing r e g i o n s of the U.S. The Bureau of A l c o h o l , Tobacco, and Firearms, enforce production l o c a t i o n r e g u l a t i o n s which g r e a t l y i n h i b i t i n t e r - v i n t n e r cooperation i n s h a r i n g equipment. Summary Time-honored methods and techniques continue to be improved by the compelling i n f l u e n c e of problems e x p l a i n e d and s o l v e d by s c i e n c e . The a p p l i c a t i o n of c u r r e n t technology across every d i s c i p l i n e and phase of wine p r o d u c t i o n r e s u l t s i n contemporary wines being the h i g h e s t q u a l i t y ever r e l e a s e d by the i n d u s t r y . Technological developments in progress promise to provide new a p p l i c a t i o n s f o r even greater wine a p p r e c i a t i o n .

Literature Cited (1)

Boone, C.; Bussey, H.; Greene, D.; Thomas, D.Y.; Vernet, T. Yeast k i l l e r toxin: s i t e directed mutations implicate the precursor protein as the immunity component. Cell 1986, 46, 105-13.


8. VINE (2)

(3)


(4)

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(10) (11) (12) (13) (14)

(15)


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Brenna, O . ; DeVecchi, S. Evaluation of protein and phenolic content in must and wine. 1. Assay of soluble proteins. Ital. J. Food Sci. 1990, 4, 269272. Duitschaever, C . L . ; Alba, J.; Buteau, C . ; A l l e n , B. Riesling wines made from must concentrated by reverse osmosis. I. Experimental conditions and composition of musts and wines. Am. J. Enol. Vitic. 1991, 42, 1925. Eschenbruch, R. H S formation - The continuing problem during winemaking fermentation technology. Australian Society of Viticulture and Oenology Proceedings 1983, 79-87. Flores, J.H.; Heatherbell, D . A . ; Henderson, L.A.; McDaniel, M.R. U l t r a f i l t r a t i o n of wine: Effect of ultrafiltration on the aroma and flavor characteristics of white r i e s l i n g and gewurztraminer wines. Am. J. Enol. Vitic. 1991, 42, 91-96. Panagiotakopoulou, V . ; Morris, J.R. Chemical additives to reduce browning in white wines. Am J. Enol. Vitic. 1991, 42, 255-260. Pompei, C. Le sucre de r a i s i n . Aspects technologiques. O.I.V. Bulletin 1982, 611, 25-52. Robredo, L . M . ; Junquera, B . ; Gonzales-Sanjose, M . L . ; Rarron, L . J . R . Biochemical events during ripening of grape berries. I t a l . J. Food Sci. 1991, 3, 173-80. Sims, C . A . ; Bates, R . P . ; Mortensen, J . A . Effects of must polyphenoloxidase a c t i v i t y and timing of s u l f i t e addition on the color and quality of V i t i s rotundifolia and Euvitis hybrid white wines. Am. J. Enol. Vitic. 1991, 42, 128-132. van Vuuren, H . J . H . ; Jacobs, C . J . K i l l e r yeasts in the wine industry: A review. Am. J. Enol. Vitic. 1992, 43, 119-128. Vine, R.P. In Commercial Winemaking; AVI/Van Nostrand Reinhold: New York, NY, 1981. Vine, R.P. Making sense of fining. Indiana Wine Grape Council Wine Lines, Summer 1992. Vine, R.P. The use of new technology in commercial winemaking. Food Technology International Europe 1987, 146-149. Vradis, I.; Floros, J. Membrane separation processes for wine dealcoholization and quality improvement. Proceedings of 7th International Conference in Food Science & Technology, 1992. Zoecklein, B.W.; Fugelsang, K . C . ; Gump, B . H . ; Nury, F . S . In Production Wine Analysis; AVI/Van Nostrand Reinhold: New York, NY, 1990. 2

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