Quality of Selected Fruits and Vegetables of North America

6 Apple Quality Characteristics as Related to Various Processed Products R. L. LA BELLE

Downloaded by TUFTS UNIV on March 5, 2017 | http://pubs.acs.org Publication Date: November 11, 1981 | doi: 10.1021/bk-1981-0170.ch006

New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456

Apples, by virtue of being widely grown, amenable to long storage, and both bland of flavor and firm of texture, are possibly processed into a wider array of products than any other fruit. While these might be roughly classified as liquid, solid, and pureed (Table 1), a diversity of product type exists within each of these categories. In addition, there are differences even within products, arising from the particular processing method used, that also affect the characteristics desired in the raw product. This situation has led to some confusion in evaluating apple quality for processing and to uncertainty in establishing i t s market value. Standards, whether of federal or state origin, have been too general to serve very well the individual users concerned with a particular product or process. Consequently, there have been attempts to set up more explicit grades that better fit Table I .

Classification o f Products Processed from Apples.

LIQUID

SOLID

PUREED

c i d e r (fresh)

baked whole apple

juice (fresh or p a s t e u r i z e d )

s l i c e s or pieces :

applesauce (including baby food)

j u i c e concentrate (4:1 o r 7:1) hard (fermented) cider wine

fresh

nectar

frozen

apple b u t t e r

canned dried dehydrofrozen

vinegar jelly

rings (canned, spiced)

essence

0097-6156/81/0170-0061 $05.00/0 © 1981 American Chemical Society Teranishi and Barrera-Benitez; Quality of Selected Fruits and Vegetables of North America ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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existing needs (1), sometimes even on an individual processing plant basis. On the other hand, the potential for utilizing apples of certain quality characteristics for the most appropriate of these diverse products has been at times a distinct marketing advantage. This paper will review the raw product quality requirements of the major processed apple products and consider the pertinent measurements that may be made on fresh apples.


Apple C h a r a c t e r i s t i c s I t w i l l be u s e f u l f i r s t t o consider the many c h a r a c t e r i s t i c s i n which apples may d i f f e r on account o f v a r i e t y , m a t u r i t y , o r post-harvest c o n d i t i o n . Most people are f a m i l i a r w i t h and able t o i d e n t i f y by s i g h t s e v e r a l o f the v a r i e t i e s commonly marketed o r grown i n t h e i r own r e g i o n , and t o remember a few o f t h e i r more obvious q u a l i t y a t t r i b u t e s as w e l l . They might even have some i d e a o f how these f a c t o r s change as the f r u i t progresses through maturation on the t r e e o r r i p e n s a f t e r h a r v e s t . The I n t e r n a t i o n a l Apple I n s t i t u t e l i s t s o n l y 14 major v a r i e t i e s i n a recent survey of storage h o l d i n g s nationwide ( 2 ) , and these would be the best known. "~ Growers and processors o f apples are e s p e c i a l l y knowledgeable about the c h a r a c t e r i s t i c s o f importance t o f i n a l product y i e l d and q u a l i t y among these v a r i e t i e s . However, i n p r a c t i c e only a few of these f a c t o r s are measured and taken i n t o account i n a s s i g n i n g market value o r i n d i r e c t i n g the f r u i t t o usage i n one product o r another. In research we have been more p a i n s t a k i n g , no doubt t o the p o i n t o f i m p r a c t i c a l i t y , i n d e f i n i n g and measuring apple q u a l i t y f o r p r o c e s s i n g , as discussed a t length i n t h i s paper. Regardless o f whether a l l such f a c t o r s are a c t u a l l y measured, an awareness o f t h e i r e f f e c t s can be v a l u a b l e t o the i n d u s t r y . Damage and decay. Damage t o the f r u i t while s t i l l on t h e t r e e may r e s u l t from i n s e c t s , d i s e a s e , weather ( i n c l u d i n g h a i l and wind), and machine operations - which together r e s u l t i n misshapen f r u i t , scar t i s s u e , and p o s s i b l y i n s e c t r e s i d u e . We might even i n c l u d e e x t e r n a l spray r e s i d u e i n t h i s category. Some o f the damaged f r u i t , e s p e c i a l l y i f decayed, w i l l f a l l t o the ground and be f o r t u i t o u s l y excluded from the harvest (unless p i c k e d up again by man o r machine). The r e l a t i v e l y rough harvest by hand o f f r u i t d e s t i n e d f o r p r o c e s s i n g o r d i n a r i l y r e s u l t s i n many shallow b r u i s e s , w h i l e machine-harvest by shaking the t r e e u s u a l l y i n f l i c t s a g r e a t e r number o f cuts and punctures. The b r u i s e s d o n t worsen during storage o f the harvested f r u i t , but skin-breaks permit m i c r o b i a l e n t r y t h a t , depending very much on storage temperature, leads i n time t o r o t (decay, o r s p o i l a g e ) . The b r u i s e d , d i s c o l o r e d t i s s u e and minor decay may be trimmed o r screened out during p r o c e s s i n g , a f f e c t i n g y i e l d o n l y s l i g h t l y though i n c r e a s i n g l a b o r - c o s t ; but extensive decay may i n t e r f e r e w i t h p e e l i n g , l e a d i n g t o t o t a l l o s s o f the f r u i t , o r a f f e c t the f

Teranishi and Barrera-Benitez; Quality of Selected Fruits and Vegetables of North America ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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f l a v o r , c o l o r , or s h e l f - l i f e of a j u i c e or puree, i f not removed. Losses of " u t i l i z a b l e m a t e r i a l " may be as h i g h as 20 percent i n badly handled and i n d i f f e r e n t l y s t o r e d apples ( 3 ) . S i z e and shape. Apple s i z e has been t r a d i t i o n a l l y expressed as diameter ranges ( i n f r a c t i o n a l inches) based on the openings i n the endless-conveyor grading chains used i n the p l a n t . P r i c i n g of these s u c c e s s i v e size-grades i s commonly stepped down at the small end. The predominant s i z e i s 2-3/4 to 3 i n c h e s , and a p r i c i n g p e n a l t y may be e s t a b l i s h e d below t h i s or some s m a l l e r s i z e - t y p i c a l l y a 2-1/2-inch minimum. A l t e r n a t i v e l y , the number of f r u i t i n a hundredweight may be counted, reducing s i z e i d e n t i f i c a t i o n to a s i n g l e number r a n g i n g , among eleven commerciallyimportant v a r i e t i e s i n New York ( 4 ) , from about 200 to 400 (apples per cwt). In research s i z e may a l s o be expressed as the u n i t weight i n grams of a s i n g l e f r u i t (from 100 to 200 g ) . Apple shape v a r i e s from o b l a t e to c o n i c , expressed most simply by an i n c r e a s e i n r a t i o of height to diameter i n the range .80 to .95. In the h i g h range there may be d i f f i c u l t y i n o r i e n t i n g the f r u i t i n automatic p e e l i n g machinery. D e v i a t i o n s from the d e s i r a b l e uniform roundness, such as pronounced r i b b i n g and e c c e n t r i c or skewed core a x i s , are more d i f f i c u l t to evaluate but probably not common or important enough to bother w i t h . The diameter of the f i v e - l o b e d a r r a y of seed pockets, l i n e d w i t h hard, u n p a l a t a b l e c a r p e l t i s s u e , does vary among c u l t i v a r s to an important extent (18 to 27 mm) and i s a f a c t o r i n the completeness o f i t s removal from the product. S p e c i f i c g r a v i t y . Apples d i f f e r from most f r u i t i n having a random network of voids or passages among the t i s s u e c e l l s , amounting to as much as 20 to 25 per cent of t i s s u e volume ( 5 ) . Together w i t h the seed pocket, t h i s space, f i l l e d w i t h a i r o r r e s p i r a t o r y gasses, lowers the s p e c i f i c g r a v i t y w e l l below 1.0 ( t y p i c a l l y .75 to .85) and accounts f o r the f a m i l i a r o b s e r v a t i o n t h a t apples bob about i n water, as do a l s o s l i c e s prepared from them. This a t t r i b u t e has s e v e r a l important r a m i f i c a t i o n s , t o be d i s c u s s e d . S p e c i f i c g r a v i t y i s s t r o n g l y i n f l u e n c e d by apple v a r i e t y , most f a m i l i a r l y a f f e c t i n g weight per b u s h e l , although t h i s i s not i n i t s e l f of profound p r o c e s s i n g s i g n i f i c a n c e . C o l o r . S k i n - c o l o r p l a y s only a minor r o l e , though l i m i t i n g the u s e f u l n e s s of some red v a r i e t i e s f o r p r o c e s s i n g . Red s k i n imparts c o l o r to the f l e s h when cooked w i t h i t and even, i f a p a r t i c u l a r l y "bleeding r e d " t h a t penetrates t h r e a d l i k e i n t o the f l e s h , to the u s u a l cold-pressed j u i c e . Since the red anthocyanin pigments are u n s t a b l e , t u r n i n g brown d u r i n g the u s u a l two-year s h e l f - l i f e of u n r e f r i g e r a t e d canned products, i t s not even a p r a c t i c a l way to o b t a i n an i n t e n t i o n a l l y pink sauce or j u i c e . C a t e g o r i z a t i o n of apples as red-skinned, as opposed to the more inocuous green or y e l l o w , i s u s u a l l y s u f f i c i e n t d e s c r i p t i o n , w i t h l i t t l e n e c e s s i t y f o r more c l o s e l y q u a n t i f y i n g the redness. f


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F l e s h - c o l o r v a r i e s from n e a r l y w h i t e , sometimes t i n g e d w i t h green, through v a r i o u s i n t e n s i t i e s o f y e l l o w . This may r e a d i l y be measured as the hue, chroma, and b r i g h t n e s s o f r e f l e c t e d c o l o r , as w i t h the Hunter C o l o r Meter (Hunterlab, 9529 Lee Highway, F a i r f a x , VA 22030), i f precautions are taken against the sometimes r a p i d darkening o f f r e s h l y - c u t apple t i s s u e . These three parameters o f f l e s h - c o l o r have a d i r e c t b e a r i n g on the r e s u l t i n g product c o l o r , g u i d e l i n e s f o r which may vary from one processor o r marketing area to another. A l i g h t , b r i g h t y e l l o w i s u s u a l l y but not u n i v e r s a l l y p r e f e r r e d . Ranges o f the Hunter c o l o r values a r e : hue (a/b) = (-).05-.45; chroma (v&* + b*) = 15-32; b r i g h t n e s s (L) = 82-91. Firmness (pressure t e s t ) . The t e x t u r e o f f r e s h apples has been measured f o r f i f t y years by use o f the simple spring-loaded penetrometer developed by Magness and T a y l o r i n 1925 ( 6 ) . Two commercial v e r s i o n s are i n common use both i n research and indust r y : the l i n e a r - s c a l e instrument o f the B a l l a u f Mfg. Co. and the c i r c u l a r - d i a l " E f f e g i . " o f I t a l i a n manufacture. While the " p r e s s u r e - t e s t e r " has f r e q u e n t l y been used as a guide t o readiness f o r harvest ( m a t u r i t y ) , i t i s much more dependable i n monitoring post-harvest r i p e n i n g , o r i n d e f i n i n g the c o n d i t i o n o f the f r u i t a f t e r harvest as a guide t o s a l e o r p r o c e s s i n g use. This f o l l o w s from the t y p i c a l shape o f t h e curve o f p r e s s u r e - t e s t reading ( i n l b o r kg) against time - n e a r l y f l a t w i t h only a s l i g h t negative slope w h i l e decreasing t o about 20 lb/9 kg through maturation and h a r v e s t , then s t e e p l y negative d u r i n g the middle stage o f r i p e n i n g and l e v e l i n g o f f again t o approach some low l e v e l o f firmness (9 l b / 4 kg) a s s y m p t o t i c a l l y . In commerce the values are s t i l l commonly given i n l b . ."Pressure t e s t " i s something o f a misnomer, as i t i s a f o r c e , equal t o the r e s i s t a n c e t o shear and crushing under the s l i g h t l y convex 7/16-inch diameter t i p , t h a t i s measured and not pressure i n the usual p h y s i c a l o r engineering sense. I t s widespread use can be explained by i t s s i m p l i c i t y and easy a d a p t a b i l i t y t o use i n the orchard o r p l a n t . Furthermore, i t does provide a reasonably good c o r r e l a t i o n - somewhat dependent on v a r i e t y w i t h both p e e l a b i l i t y and f i n a l product t e x t u r e i n the case o f apple s l i c e s o r sauce and w i t h p r e s s a b i l i t y f o r c i d e r and j u i c e . In i n d u s t r y a common mistake i s t o i n c l u d e too few apples i n t h e sample e v a l u a t e d , 10 t o 25 being a u s e f u l sample s i z e ( 7 ) . The usual p r o c e s s i n g range i s 11 t o 18 lb/5 t o 8 kg. S o l u b l e and t o t a l s o l i d s . The common use o f s o l u b l e s o l i d s to d e f i n e f r e s h apple q u a l i t y came about i n response t o the need f o r a more r e l i a b l e and meaningful guide t o readiness f o r h a r v e s t . A u s e f u l estimate o f percent s o l u b l e s o l i d s - mostly sugars, but a l s o i n c l u d i n g the usual 1/4 t o one percent o f organic a c i d - i s r e a d i l y determined as the e q u i v a l e n t °Brix, even i n the f i e l d , by a r e p r e s e n t a t i v e drop o f j u i c e i n a hand r e f r a c t o m e t e r . The usual


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range i s 10 t o 15° B r i x . T o t a l s o l i d s , or dry weight, i s measured by d r y i n g a very small a l i q u o t of d i l u t e pureeed m a t e r i a l i n a vacuum oven, although u s e f u l estimates w i t h perhaps l e s s sampling e r r o r have been obtained i n our l a b o r a t o r y by f r e e z e - d r y i n g l a r g e r samples (300 g) to about .5% moisture. T o t a l s o l i d s average 1.4% g r e a t e r than s o l u b l e s o l i d s , v a r y i n g from t h i s i n a p a t t e r n not yet w e l l - d e f i n e d . A c i d i t y and pH. These chemical and f l a v o r f a c t o r s are e a s i l y determined i n the l a b o r a t o r y , i f not i n the f i e l d , and are f r e quently used i n the p r o c e s s i n g p l a n t as w e l l as i n r e s e a r c h t o evaluate both apple c o n d i t i o n and p o t e n t i a l product f l a v o r . The t o t a l t i t r a t a b l e a c i d i t y ( p r i n c i p a l l y m a l i c ) , s t a r t i n g at a l e v e l c h a r a c t e r i s t i c of the v a r i e t y , p r o g r e s s i v e l y drops o f f d u r i n g both maturation and r i p e n i n g t o provide a u s e f u l index of those succ e s s i v e developments. Since a c i d i t y i s changing i n the opposite d i r e c t i o n from s o l u b l e s o l i d s content d u r i n g maturation, the r a t i o of the two, v a r i o u s l y r e f e r r e d to as " s u g a r - a c i d " , " B r i x - a c i d " , o r " s o l u b l e s o l i d s - a c i d " , s h i f t s r a p i d l y and i s more u s e f u l as a guide to readiness f o r harvest than i s pressure t e s t ( 8 ) . However, the f a m i l i a r caveat concerning seasonal v a r i a t i o n must be g i v e n ; the l e v e l s of e i t h e r or both parameters of the r a t i o may d i f f e r a p p r e c i a b l y from one year to the next, even i n f r u i t from a p a r t i c u l a r orchard, so t h a t bench-marks should be e s t a b l i s h e d e a r l y i n the season f o r the ensuing changes d u r i n g maturation. The measurement of pH seems more r e a d i l y and a c c u r a t e l y accomplished w i t h present meters than a generation ago, and i t i s commonly used to monitor the endpoint of the acid-base t i t r a t i o n i n p l a c e of the c o l o r change of an i n d i c a t o r . I t s r e l a t i v e r o l e i n the p e r c e p t i o n of a c i d i t y or t a r t n e s s has been r e c e n t l y s t u d i e d i n wine from grapes ( 9 ) , where the mix of organic a c i d s ( m a l i c , t a r t a r i c , and c i t r i c ) i s d i f f e r e n t , but t h i s needs f u r t h e r d e f i n i t i o n i n apple. In wine i t i s secondary to t o t a l a c i d i t y i n i t s e f f e c t on f l a v o r . The pH value u s u a l l y l i e s between 3.2 and 3.8, w i t h some e x c u r s i o n s , even among apple v a r i e t i e s used i n commerce, o u t s i d e that range. On the h i g h s i d e such abberations may s i g n a l that the usual means of p r e s e r v a t i o n of a c i d foods - f o r example, h o t - f i l l without subsequent r e t o r t i n g - may not s u f f i c e . A c i d i t y i s of s p e c i a l importance t o the f l a v o r of processed apple products i n t h a t , l i k e sweetness, i t remains s u b s t a n t i a l l y unchanged during normal canning, f r e e z i n g , or d r y i n g , w h i l e more s u b t l e v o l a t i l e f l a v o r elements are l i k e l y to degrade or d i s appear . Other f l a v o r elements. Fresh apple f l a v o r i s c h a r a c t e r i z e d by what i s apparently a l a r g e number of organic compounds, present i n t r a c e amounts, t h a t are most r e a d i l y determined by chromatographic methods (10). Many of these v o l a t i l e compounds w i l l be g r e a t l y reduced or absent i n the processed product, unless r e p l a c e d by the essence obtained by s t r i p p i n g i n the i n i t i a l stages



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of j u i c e c o n c e n t r a t i o n . V a r i e t i e s having f a m i l i a r v o l a t i l e f l a v o r notes t h a t d i s t i n g u i s h them when f r e s h are thereby reduced to a more bland apple f l a v o r , together w i t h a c h a r a c t e r i s t i c balance of sweetness and t a r t n e s s . However, t h i s has i t s advantages i n the market p l a c e , where u n i f o r m i t y r a t h e r than d i v e r s i t y i s o r d i n a r i l y d e s i r e d , o f f e n d i n g no one i f f a l l i n g somewhat short of premium q u a l i t y . Laboratory e v a l u a t i o n of apple f l a v o r i s s t i l l a r e l a t i v e l y undeveloped s c i e n c e , but there i s l i t t l e i n c e n t i v e to i d e n t i f y and p r o t e c t these t r a c e f l a v o r elements as matters now stand. Probably no concensus e x i s t s f o r what cons t i t u t e s high q u a l i t y i n apple f l a v o r d e s p i t e comments, not uncommonly heard, d e p l o r i n g i t s absence. T o t a l t a n n i n or polyphenols can be determined i n apple by permanganate t i t r a t i o n without too much d i f f i c u l t y , and t h i s has some usefulness i n e v a l u a t i n g the l e v e l of a s t r i n g e n c y t h a t p l a y s a t r a d i t i o n a l r o l e i n fermented c i d e r , p a r t i c u l a r l y of the B r i t i s h or European type. However, the chemistry seems not yet to be w e l l - d e f i n e d (11, 12), so t h a t the v a r i o u s r o l e s of the t a n n i c m a t e r i a l s - p r o v i d i n g the s e n s a t i o n of a s t r i n g e n c y and sometimes a b i t t e r f l a v o r note; causing more or l e s s browning of c o l o r ; a s s i s t i n g i n a u t o - c l a r i f i c a t i o n of j u i c e , c i d e r , and wine; and e i t h e r promoting or preventing u n d e s i r a b l e hazes - are not w e l l p r e d i c t e d by the usual t e s t s . The importance of t h i s chemistry seems l i k e l y to grow along w i t h the s o p h i s t i c a t i o n of p r o c e s s i n g and consumer products. Meanwhile, the l e s s s a i d here by someone who i s not a chemist, the b e t t e r f o r the reader. Rate of browning. O x i d a t i o n of polyphenol s u b s t r a t e i n the presence of a c t i v e polyphenolase and oxygen causes browning of f r e s h l y - c u t or crushed apple t i s s u e t h a t may be d i s c e r n i b l e i n l e s s than f i v e minutes at room temperature. There i s c o n s i d e r a b l e v a r i a t i o n among, and even w i t h i n , c u l t i v a r s i n the r a t e at which browning proceeds due to d i f f e r e n c e s i n the l e v e l or chemical nature of the s u b s t r a t e or of the enzyme i t s e l f ; i t has not been made c l e a r which i s the more l i k e l y c o n s t r a i n t . The r a t e of browning on a f r e s h l y - c u t surface of apple f l e s h has been determined i n terms of the change i n r e f l e c t a n c e (AL) w i t h the Hunter c o l o r meter and found to range from 1 to 8 u n i t s i n 10 min. O x i d a t i v e browning may be no drawback to such products as c i d e r , apple b u t t e r , or vinegar but i s u n d e s i r a b l e i n s l i c e s , sauce, j u i c e concentrate, and some s t y l e s of j u i c e . F o r t u n a t e l y , i t can be c o n t r o l l e d by r a p i d thermal i n a c t i v a t i o n of the enzymes, by chemical i n h i b i t i o n - as w i t h a s c o r b i c a c i d or s u l f u r d i o x i d e , or to a l e s s e r extent by e x c l u d i n g oxygen, m a i n t a i n i n g low temperat u r e , or minimizing the extent of ruptured c e l l s . Apple j u i c e c o l o r i s a f f e c t e d both by v a r i e t a l f l e s h c o l o r and by the degree of browning permitted during p r o c e s s i n g . The i n t e n s i t y of s t a b i l i z e d brown c o l o r i n a c l e a r l i q u i d product can be measured s p e c t r o p h o t o m e t r i c a l l y as absorbance of t r a n s m i t t e d l i g h t and expressed as o p t i c a l d e n s i t y @ 410 nm or merely compared to gradi n g standards, such as the USDA Honey C o l o r Comparometer.



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J u i c i n e s s . The ready s e p a r a t i o n o f j u i c e from the f l e s h , touted as d e s i r a b l e i n an apple eaten out o f hand, might a l s o be advantageous i n the p r e s s i n g o f apples f o r j u i c e , but not t o the s l i c e - o r sauce-packer. While some i n d i r e c t a t t e n t i o n has been p a i d t o i t i n observations o f p r e s s a b i l i t y , sauce c o n s i s t e n c y and y i e l d , and the drained weight o f f r e s h o r f r o z e n s l i c e s , appare n t l y no one has bothered t o measure j u i c e s e p a r a t i o n from f r e s h l y cut o r crushed apple t i s s u e d i r e c t l y i n a l a b o r a t o r y procedure. V a r i e t i e s are g e n e r a l l y known t o lean one way o r the other i n the tendency t o be j u i c y and t o be valued a c c o r d i n g l y by the processor f o r the e f f e c t i t might have on y i e l d o r q u a l i t y . A l s o , r i p e n i n g has up t o a p o i n t , the e f f e c t o f i n c r e a s i n g j u i c e s e p a r a t i o n . I t ' s p o s s i b l e t h a t the development o f an a p p r o p r i a t e l a b o r a t o r y t e s t would l e a d t o i n t e r e s t i n g and more a c c u r a t e l y known c o r relations . Q u a l i t y Factors Important t o D i f f e r e n t Processed

Products

What the raw product should be l i k e t o provide s u i t a b l e y i e l d and q u a l i t y i s d i c t a t e d as much as anything by the f i n a l form o f the processed product. The u n i t operations themselves and the nature o f the machines and p r o c e s s i n g media o r chemicals used to implement them have a d d i t i o n a l requirements and e f f e c t s . Together they determine, f o r i n s t a n c e , whether there w i l l be o p p o r t u n i t y t o exclude u n d e s i r a b l e o r damaged p a r t s o f the f r u i t , whether the t e x t u r e needs t o be e x t r a f i r m or the s o l i d s content p r e f e r a b l y h i g h , and whether such f a c t o r s as browning r a t e o r j u i c i n e s s are l i k e l y t o be problems. Each product seems t o have a d i f f e r e n t combination o f requirements, as shown by the r a t i n g s i n Table 2 and a m p l i f i e d i n the t e x t t o f o l l o w . Baked whole apple. Although a s p e c i a l t y item o f low volume and small importance, i t ' s i n c l u d e d i n t h i s p r e s e n t a t i o n as the s o l e r e p r e s e n t a t i v e o f the n e a r l y whole apple ( i f we may ignore the candied p r o d u c t ) . U n i f o r m i t y o f s i z e and f i r m , cohesive t e x t u r e seem t o be paramount c o n s i d e r a t i o n s . Along w i t h the core, about t w o - t h i r d s o f the p e e l should be removed, s t a r t i n g from the s m a l l e r blossom-end. This a i d s i n h o l d i n g the apple together when cooked but avoids the problems w i t h s k i n that i s e i t h e r too tough to cut w i t h a spoon o r t h a t s p l i t s at random. F l e s h and s k i n c o l o r are probably matters o f t a s t e , and the degree o f darkening i s r e l a t i v e l y unimportant, unless the prepared apples are f r o z e n f o r baking l a t e r . A small seed pocket and a n o n - j u i c y c h a r a c t e r would be advantageous. Appreciable t a r t n e s s i s a l s o d e s i r a b l e t o o f f s e t the c o n s i d e r a b l e amount of sweetener added i n p r e p a r a t i o n f o r the t a b l e .



low

small

high

not

yellow

Shape (ht./diam.)

Seed pocket s i z e

Specific gravity

Skin color

Flesh color

red

med.-lg.

Size

low

medium

Condition : ripeness

decay

full

Maturity

low

V

Variety

damage

Desired level

Baked apple

Fresh or Frozen

Canned

Dried or Dehydrofrozen

Apple sauce

++

Cider $ Juice

Importance of Various Q u a l i t y Factors to D i f f e r e n t Processed Products.

Quality factor

Table 2.


++

Juice oncentrate

Hard cider ξ Wine

Teranishi and Barrera-Benitez; Quality of Selected Fruits and Vegetables of North America ACS Symposium Series; American Chemical Society: Washington, DC, 1981. +

++ ++

high

high

medium

medium

medium

low

low

medium

Soluble s o l i d s

Total s o l i d s

Total acid

pH

Volatile flavor

Tannins

Rate o f browning

Juiciness

-

++

+

+

+

++

Fresh o r Frozen

+

++

++

+++

Canned

++

-

-

++

++

++

++

++

+

Apple sauce

+++

+++

+++

++

Dried o r Dehydrofrozen

+

++

+

Cider $ Juice

+

+

-

-

a) v a r i e t a l importance i s based on the usual p r a c t i c e o f marketing as s i n g l e v a r i e t i e s without blending b) i f d i c e d r a t h e r than s l i c e d , the l a r g e r the b e t t e r , so long as s t i l l machine-peelable

+

--

•

Hard cider ξ Wine

-

+

+++

Juice oncentrate

+ ++ +++ = degree o f importance - — = importance opposite t o normally d e s i r e d l e v e l i n d i c a t e d i n the second column

—

++

+++

firm

Firmness (.pressure t e s t )

Baked apple

Desired level

Quality factor

Table 2 (cont.)



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Fresh o r f r o z e n s l i c e s . F u l l y mature, w e l l - r i p e n e d apples o f a s i n g l e v a r i e t y are r e q u i r e d t o provide the premium q u a l i t y expected o f t h e f r o z e n product. To a l e s s e r extent t h i s i s a l s o t r u e o f the f r e s h s l i c e s t h a t are l i g h t l y t r e a t e d w i t h a n t i o x i d a n t f o r a s h e l f - l i f e i n c o l d - s t o r a g e o f two t o f o u r weeks. E i t h e r form i s best produced from f a i r l y p e r f e c t , undamaged f r u i t t o avoid extensive hand-trimming. An e a s i l y p e e l a b l e shape and small seed pocket w i l l help t o minimize r e s i d u a l peel and c a r p e l t h a t are a l s o u n d e s i r a b l e and cause f o r down-grading under the U.S. Standards. Medium-size wedge ( r a d i a l - c u t ) s l i c e s are p r e f e r r e d because l a r g e s l i c e s tend t o be underblanched (with brown centers) and a l s o t o have excessive r e s i d u a l c a r p e l attached. When a s u l f i t e a n t i o x i d a n t i s used, there i s l i k e l y t o be f a s t e r , more complete p e n e t r a t i o n t o the s l i c e centers i f the extent o f v o i d s i n t h e t i s s u e i s great and the s p e c i f i c g r a v i t y t h e r e f o r e low. The tendency t o browning d i s c o l o r a t i o n should be s l i g h t i n order t o i n s u r e most acceptable c o l o r , e s p e c i a l l y i n the l i g h t l y - s u l f i t e d , f r e s h s l i c e s . There i s a premium on f i r m , cohesive t e x t u r e t h a t w i l l encourage s l i c e i n t e g r i t y throughout p r o c e s s i n g and l a t e r u t i l i z a t i o n i n the bakery. J u i c i n e s s should be minimal t o y i e l d a high drained weight o f frozen-thawed product or o f the f r e s h product a f t e r r e f r i g e r a t e d storage. Canned s l i c e s . The requirements f o r canning apples are only s l i g h t l y d i f f e r e n t from those d e s c r i b e d f o r f r e s h and f r o z e n . Because o f the s e v e r i t y o f thermal p r o c e s s i n g i n the usual s o l i d l y - p a c k e d #10 can, t h e apples have a g r e a t e r need t o be e x t r a f i r m . This i s o f t e n obtained by d e l i b e r a t e s e l e c t i o n o f hard v a r i e t i e s , h a r v e s t i n g at e a r l y m a t u r i t y , o r p r o c e s s i n g soon a f t e r h a r v e s t . Apples o f high s p e c i f i c g r a v i t y would probably help i n o b t a i n i n g the r e q u i r e d 7-lb f i l l , although t h i s i s p a r t l y a matter of the thermal o r vacuum p r o c e s s i n g t h a t r e p l a c e s t i s s u e gasses w i t h l i q u i d as completely as p o s s i b l e . Flooding o f t h e t i s s u e v o i d s w i t h p r o c e s s i n g medium may o f f s e t both low s p e c i f i c g r a v i t y and excessive l o s s o f j u i c e . A f u r t h e r reason f o r the replacement of gasses i s t o prevent e a r l y c o r r o s i o n o r f a i l u r e by p i n - h o l i n g of the can l i n i n g due t o oxygen remaining i n the product o r headspace. S l i c e s thoroughly cooked i n a water medium w i l l be e s p e c i a l l y bland i n f l a v o r , suggesting t h a t an a p p r e c i a b l y t a r t apple be used. D r i e d o r dehydrofrozen p i e c e s . Dried apple i s produced at two p r i n c i p a l moisture l e v e l s : 18 - 24% f o r the t r a d i t i o n a l "evaporated apples" and 2 - 5 % f o r the more f u l l y d r i e d product. Dehydrofrozen p i e c e s are commonly d r i e d t o h a l f t h e i r o r i g i n a l weight and then preserved from m i c r o b i a l s p o i l a g e by f r e e z i n g . These products i n c l u d e the i n c r e a s i n g l y popular d i c e d form used i n f r i e d p i e s , t u r n o v e r s , and other small bakery items. A high c u t y i e l d o f more uniform d i c e s can be obtained w i t h very l a r g e apples as long as they can be adequately machine-peeled. The s m a l l e r p i e c e s i z e common t o these d r i e d products i s an advantage i n t h a t



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71

l e s s thorough trimming o f the peeled apple i s necessary. Bruised t i s s u e i s more u n s i g h t l y than u n p a l a t a b l e , so that the r e d u c t i o n o f damaged areas t o more innocuous b i t s by the s m a l l e r cut p a r t l y a l l e v i a t e s the need f o r trimming. This i s o b v i o u s l y l e s s t r u e o f decay than o f simple b r u i s e s . The use o f a s u l f i t e a n t i o x i d a n t i s n e a r l y u n i v e r s a l , but because o f the small p i e c e s i z e , s u l f i t e p e n e t r a t i o n i s not so c r i t i c a l as i n s l i c e s . Hence, the g r e a t e r t i s s u e voids a s s o c i a t e d w i t h low s p e c i f i c g r a v i t y may be l e s s advantageous and perhaps counter-productive i n p e r m i t t i n g the SO^ t o be swept away during drying, leaving i n s u f f i c i e n t r e s i d u a l to insure e f f e c t i v e a n t i oxidant p r o t e c t i o n against browning, o x i d a t i v e o r otherwise, i n the d r i e d product during storage. A secondary s u l f i t e treatment a f t e r d r y i n g and e q u i l i b r a t i o n and before or during packaging i s o f t e n p r a c t i c e d f o r that reason. The g r e a t e r the i n i t i a l s o l i d s content i n the f r e s h apple, the l e s s d r y i n g needs t o be done t o reach the d e s i r e d low moisture l e v e l . In a time o f s t e a d i l y i n c r e a s i n g f u e l c o s t , t h i s can be a r e a l advantage. On the other hand, a low t o moderate a c i d i t y w i l l a l s o be concentrated by the d r y i n g process t o a r e l a t i v e l y intense l e v e l that may i n part p e r s i s t through the o r d i n a r i l y incomplete (70%) r e c o n s t i t u t i o n i n the bakery product. This e f f e c t i s probably the main reason why d r i e d foods have an i l l - d e s e r v e d r e p u t a t i o n f o r being e s p e c i a l l y t a s t y , whereas i n t r u t h much o f the v o l a t i l e f l a v o r w i l l have been i r r e t r i e v a b l y l o s t i n d r y i n g . A low r a t e o f browning i s h e l p f u l s i n c e h e a t i n g the pieces t o e f f e c t d r y i n g may f o l l o w c l o s e on the heels o f a n t i o x i d a n t t r e a t ment - before i t has had time t o become f u l l y e f f e c t i v e . An o l d e r procedure used w i t h the l a r g e r wedge-slices allowed some time f o r s u l f i t e p e n e t r a t i o n t o be completed before d r y i n g was s t a r t e d , but t h i s l e d t o excessive s e p a r a t i o n o f s o l i d s - b e a r i n g j u i c e from the t i s s u e , the i n t e g r i t y o f which i s attacked by the s u l f i t e . This 'weeping* from the cut s u r f a c e s , a r i s i n g a l s o from the n a t u r a l j u i c i n e s s o f the apple, i s anethema i n the d r y e r , where i t may cause excessive s t i c k i n g o f pieces t o the conveying s u r f a c e , besides reducing y i e l d o f d r i e d product. Applesauce. This d i s t i n c t l y North American product has only r e c e n t l y y i e l d e d f i r s t p l a c e i n apple u t i l i z a t i o n t o j u i c e products. Various i n i t s c o l o r , f l a v o r , and t e x t u r e , i t enjoys f a v o r among a wide p u b l i c . The f a c t that not everyone l i k e s the same s t y l e o f sauce somewhat complicates the c o r r e l a t i o n o f raw and processed product attempted i n t h i s paper. S t i l l , c e r t a i n elements are h e l d i n common. Blending i s u s u a l l y , though not always, p r a c t i c e d both t o improve sauce q u a l i t y and t o make i t more uniform over the season o f pack. Golden D e l i c i o u s and Mcintosh are made i n t o s i n g l e v a r i e t y sauces, perhaps not so much because they are e s p e c i a l l y good f o r the purpose as t h a t they are well-known t o the consuming p u b l i c and a v a i l a b l e i n l a r g e q u a n t i t y , o f t e n as packing-house



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AND

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c u l l s from the more well-deserved marketing of these v a r i e t i e s f r e s h . Gravenstein i s a l s o used i n a s i n g l e - v a r i e t y sauce to somewhat b e t t e r e f f e c t . Unless an e s p e c i a l l y coarse or hard g r a i n i n e s s of t e x t u r e i s d e s i r e d , f l a v o r i s l i k e l y t o be best i n f u l l y matured and w e l l ripened f r u i t . Quite a b i t of the v o l a t i l e f l a v o r that maturation and r i p e n i n g develop i s l o s t i n cooking by a s o r t of steam-dist i l l a t i o n o f the p u l p . T h i s i n v o l v e s a heat t r a n s f e r - e f f i c i e n t d i r e c t contact o f steam w i t h f i n e l y - c u t apple, f o l l o w e d by cent r i f u g a l p u l p i n g through a screen w h i l e s t i l l very hot. However, a well-made sauce should r e t a i n some aroma i f these operations are e f f e c t i v e l y enclosed. Decay must be removed by hand-trimming, but much of the b r u i s e d t i s s u e and c a r p e l w i l l be e l i m i n a t e d as waste d u r i n g p u l p i n g and f i n i s h i n g through s u c c e s s i v e f i n e screens (1/8-inch, or l e s s ) . Red s k i n would impart i t s u n s t a b l e c o l o r to sauce d u r i n g cooking, so that commercial sauce i s r a r e l y made from unpeeled f r u i t . Since much of the s u p e r f i c i a l b r u i s e d t i s s u e a r i s i n g from normal harvest and h a n d l i n g i s removed by p e e l i n g , even y e l l o w - or green-skinned f r u i t i s c u s t o m a r i l y peeled. Cores are a l s o removed, not because of concern w i t h c a r p e l so much as to e l i m i n a t e troublesome broken seeds and dark fragments from the blossom end. Hence, y i e l d i n t h i s i n s t a n c e i s s a c r i f i c e d i n the i n t e r e s t s of q u a l i t y . Sauce c o l o r i s u s u a l l y subject to strong preference on the p a r t of the buyer or i n a p a r t i c u l a r market - whether y e l l o w , w h i t e , or green-tinged. The blend of apple v a r i e t i e s may be chosen a c c o r d i n g l y . There i s c o n s i d e r a b l e l a t i t u d e i n B r i x - a c i d r a t i o ... anywhere from 25 t o 60, and i t i s a d j u s t a b l e w i t h i n l i m i t s by the a d d i t i o n o f a v a r i a b l e l e v e l of sugar, or even of food a c i d . A recent move t o marketing applesauce at lower B r i x (15°) than the u s u a l 18 - 20° range i s p a r t l y i n response to d i e t - c o n s c i o u s consumers and p a r t l y , as at p r e s e n t , because of the p r i c e o f sugar r i s i n g above that of apple. To preserve the usual B r i x - a c i d r a t i o i n that case, apples of lower n a t u r a l a c i d i t y should be used, which i s e a s i e r to do r a t h e r than more d i f f i c u l t i n some r e g i o n s . The r a t e of browning i s important i n sauce p r o c e s s i n g , as a l i g h t , b r i g h t c o l o r i s d e s i r e d . Heating may be slow enough i n some cookers that the enhanced enzyme a c t i v i t y experienced i n the range 125 t o 160°F, p a r t way through the come-up to a cook temperature of 215°F, may permit r a p i d browning before enzyme i n a c t i v a t i o n i s accomplished. The amount of f r e e l i q u i d i n applesauce i s adjusted t o provide the proper f l o w c h a r a c t e r i s t i c s and mouthfeel. In some v a r i e t i e s , p a r t i c u l a r l y when q u i t e r i p e , the n a t u r a l s e p a r a t i o n of j u i c e from the broken c e l l s t r u c t u r e together w i t h the steam i n c o r p o r a t e d as condensate (about 15% w/w) i s more than enough, w h i l e to others water must be added w i t h the sugar, i n c r e a s i n g case y i e l d i n p r o p o r t i o n . Apple v a r i e t i e s f o r sauce are sometimes priced accordingly.



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C i d e r and j u i c e . These products are f r e q u e n t l y not d i s t i n guished i n the t r a d e , though some do i n s i s t on a d i f f e r e n c e . The f r e s h l y - p r e s s e d j u i c e o f the apple i s n a t u r a l l y more o r l e s s cloudy as w e l l as somewhat t h i c k o r syrupy i n body, and i t q u i c k l y o x i d i z e s both i n c o l o r and f l a v o r . These a t t r i b u t e s c h a r a c t e r i z e c i d e r i n the o l d e r t r a d i t i o n . Enzyme-treatment and f i l t r a t i o n that c l a r i f y the c i d e r , and i n c i d e n t a l l y degrade the p e c t i n and t h i n i t s body, render i t apple j u i c e , i n my e s t i m a t i o n . The same may be s a i d o f the use o f a n t i o x i d a n t such as a s c o r b i c a c i d to maintain the o r i g i n a l l i g h t c o l o r , o r p a s t e u r i z a t i o n that adds a cooked note t o the f l a v o r . But, depending on how s e r i o u s l y you view the i n t r u s i o n o f chemical p r e s e r v a t i v e s such as potassium sorbate o r sodium benzoate i n t o the f l a v o r , the d e f i n i t i o n o f c i d e r might be bent a l i t t l e t o i n c l u d e t h e i r use. Decay must be thoroughly removed by s o r t i n g and vigorous washing. Apart from a e s t h e t i c s and the probable i n t r o d u c t i o n o f o f f - f l a v o r , m i c r o b i a l s p o i l a g e o f the c i d e r o r j u i c e may be hastened by the f a i l u r e t o c l e a n up the raw product. There i s a l s o a t o x i c o l o g i c a l c o n s i d e r a t i o n i n the p o s s i b l e occurrence o f moId-induced p a t u l i n ( 1 3 ) . One would t h i n k there might be some c o r r e l a t i o n between the s e n s a t i o n o f j u i c i n e s s on b i t i n g i n t o an apple and the ease w i t h which a normally h i g h p r e s s - y i e l d o f 80 per cent o r more could be obtained. That may be so, but the data t o prove i t seems s c a r c e . T h i s may be a case o f "back t o the l a b o r a t o r y " . . . The r a t e and u l t i m a t e degree o f browning have l e a s t e f f e c t on the p r e p a r a t i o n o f a " n a t u r a l " l i g h t - c o l o r e d j u i c e . Since the a s c o r b i c a c i d can be added ( t y p i c a l l y at .05%) d i r e c t l y i n t o the m i l l as the apple i s f i n e l y chopped before p r e s s i n g , there i s l i t t l e d i f f i c u l t y i n c o n t r o l l i n g enzymatic browning q u i t e completely. There i s even reason t o t h i n k that the trade w i l l more r e a d i l y accept such a j u i c e i f a delay i n adding the a s c o r b i c a c i d i s p r a c t i c e d t o permit a l i t t l e i r r e v e r s i b l e browning t o develop a more r e c o g n i z a b l e l i g h t amber o r golden c o l o r . The d e s i r e d delay would depend on j u i c e temperature, oxygen c o n t a c t , and the i n t r i n s i c p o t e n t i a l o f the apple v a r i e t y f o r browning. A h i g h l e v e l o f suspended s o l i d s i n c i d e r reduces i t s t r a n s l u c e n c y , p o s s i b l y making i t appear u n a t t r a c t i v e l y muddy and c o n t r i b u t i n g t o e a r l y and excessive formation o f sediment i n the consumer package. T h i s might be considered an a r t i f a c t as much as a f a c t o r o f raw product q u a l i t y , since m i l l i n g and p r e s s i n g methods a f f e c t i t so d i r e c t l y . O v e r r i p e , o u t - o f - c o n d i t i o n f r u i t - such as i s very o f t e n used - i s a p r i n c i p a l c o n t r i b u t i n g f a c t o r . While the suspended s o l i d s may be completely removed from c l a r i f i e d j u i c e , f i l t r a t i o n e f f i c i e n c y and f i n a l j u i c e y i e l d would be a d v e r s e l y a f f e c t e d by t h e i r presence i n excess o f one or two per cent. Hazes appearing i n c l a r i f i e d j u i c e are sometimes a problem; t h e i r chemistry has been r e c e n t l y d i s c u s s e d (14, 15). Although the f l a v o r o f the apple i s c a r r i e d over i n t o c i d e r and j u i c e , at l e a s t i n terms o f sugar/acid balance, l i t t l e de-


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l i b e r a t e s e l e c t i o n of raw product i s p r a c t i c e d on t h a t account. What i s a v a i l a b l e economically i s what i s used f o r these products. But s i n c e b l e n d i n g of d i f f e r e n t v a r i e t i e s and l o t s of apples i s u s u a l , product q u a l i t y remains near some acceptable i f u n d i s t i n guished mean. In g e n e r a l , an apple r i g h t f o r e a t i n g out o f hand i s a l s o r i g h t f o r c i d e r or j u i c e , remaining a somewhat s u b j e c t i v e judgment i n t h a t sense. J u i c e concentrate. T h i s product has become an important commodity i n world t r a d e , i t s many uses not l i m i t e d j u s t t o r e c o n s t i t u t i o n i n t o s i n g l e - s t r e n g t h j u i c e . The normal 7:1 (72° B r i x ) concentrate i s convenient and economical t o s t o r e and s h i p , needing r e f r i g e r a t i o n o n l y t o reduce u s u a l browning. Its requirements f o r raw product q u a l i t y are s u b s t a n t i a l l y the same as f o r s i n g l e - s t r e n g t h j u i c e . Since brown d i s c o l o r a t i o n i s i t s e l f concentrated i n the product and added to by p o s s i b l e c a r a m e l i z a t i o n i n the evaporator and non-enzymatic browning d u r i n g long storage at ambient, i t i s even more important t o minimize enzymatic browning d u r i n g the i n i t i a l p r o c e s s i n g . As i n d r i e d apple, c o n c e n t r a t i o n p l a c e s a premium on h i g h s t a r t i n g s o l i d s , though i n t h i s case o n l y s o l u b l e s are i n v o l v e d . Hard c i d e r and wine. While apple v a r i e t y i s considered important i n these apple p r o d u c t s , i t may be mainly a matter of t r a d i t i o n . True, the B r i t i s h and European c i d e r apples are (or more a c c u r a t e l y , were) s p e c i a l s o r t s , remarkable as w e l l f o r t h e i r mean s i z e and u n p a l a t a b i l i t y f r e s h as f o r the pronounced a s t r i n g e n c y t h a t provides a d i s t i n c t i v e c i d e r f l a v o r . However, the North American market f o r a l o w - a l c o h o l (6%) hard c i d e r or apple wine i s so r e l a t i v e l y undeveloped t h a t product q u a l i t y i s not yet w e l l - d e f i n e d . Hence, some popular dessert apples - even, or e s p e c i a l l y , the s l i g h t l y a s t r i n g e n t and low-acid Red D e l i c i o u s may be q u i t e adaptable. Among the few requirements t h a t can be c l e a r l y seen at present are f u l l y mature and w e l l - r i p e n e d f r u i t (perhaps t o the p o i n t of d e c l i n i n g p r e s s a b i l i t y ) , the lower a c i d i t y a s s o c i a t e d w i t h i t , and at l e a s t some pretense of a s t r i n g e n c y t o add a d e s i r a b l e complexity t o the f l a v o r s e n s a t i o n . The choice o f carbonated or sweetened v e r s i o n s of the product, as opposed t o s t i l l or d r y , would probably r e f l e c t d i f f e r e n t l y on raw product s p e c i f i c a t i o n s . Apple wine, l e g a l l y d e f i n e d as having g r e a t e r than 7 per cent a l c o h o l by volume, would b e n e f i t from h i g h s o l u b l e s o l i d s t o reduce the need f o r added sugar. A pronounced f r u i t i n e s s might c a r r y over i n t o the f i n i s h e d wine t o b e t t e r advantage than i n hard c i d e r , l e s t the g r e a t e r a l c o h o l content predominate i n f l a v o r . As i n sweet c i d e r and j u i c e , the raw product requirements of these fermented beverages may not be d i f f i c u l t t o meet, product q u a l i t y being more c e r t a i n l y dependent on good manufacturing p r a c t i c e s .



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Other products. Of the remaining products l i s t e d i n Table 1, l e s s needs to be s a i d . Except f o r v i n e g a r , which i s l a r g e l y made from peel-and-core waste anyway, they are a l l minor uses of apple. Not much apple c h a r a c t e r i s r e t a i n e d i n such thoroughly t r a n s formed products as vinegar and apple b u t t e r . A reasonable subs t i t u t e f o r the former i s even made from s y n t h e t i c e t h a n o l , as w e l l as from other f r u i t s , w h i l e the l a t t e r i s not only given a lengthy c a r a m e l i z i n g cook but i s h e a v i l y spiced as w e l l . In each, however, a high l e v e l of f r u i t sugar would be advantageous - as the fermentable s u b s t r a t e f o r a c e t i c a c i d i n the f i r s t and as a headstart on the d e s i r e d c o n c e n t r a t i o n and t h i c k e n i n g of c o n s i s tency i n the o t h e r . The p r i n c i p a l requirement f o r s p i c e d apple r i n g s i s a f i r m apple t e x t u r e that w i l l perform w e l l as a c a r r i e r f o r the added c o l o r and f l a v o r , much the same as i n maraschino c h e r r i e s , though uniform f r u i t s i z e may a l s o be a f a c t o r . Apple j e l l y could presumably be made without a d d i t i v e s other than sugar i f p e c t i n , a c i d , and pigmentation were at the r e q u i r e d l e v e l s , as i n crabapples. Apple essence, d e r i v e d from s t r i p p i n g v o l a t i l e s from d e p e c t i n i z e d , s i n g l e - s t r e n g t h j u i c e p r i o r to i t s c o n c e n t r a t i o n , i s an undefined pot p o u r i of f l a v o r elements c h i e f l y s p e c i f i e d i n terms of i t s c o n c e n t r a t i o n or " - f o l d " . Nectar or p u l p , prepared as a s i n g l e - s t r e n g t h or somewhat concentrated homogenates of whole apple, are not p r e s e n t l y a r t i c l e s of commerce i n the United S t a t e s . However, some processes f o r and grades of applesauce have approximated t h i s s i m p l i f i e d approach, g a i n i n g i n y i e l d at the expense of q u a l i t y . Other c o n s i d e r a t i o n s . L i t t l e has been s a i d here of the r o l e of the p e c t i c substances, and the omission may be a g l a r i n g one i n view of t h e i r c e r t a i n involvement i n the q u a l i t y of many of these products. As i n the polyphenols, the chemistry i s complex and beyond the scope of t h i s review. P e c t i n i s i n t e n t i o n a l l y removed from j u i c e t o be c l a r i f i e d by employing enzymatic degradation; t h i s e f f e c t s the d e s i r e d c o l l o i d a l change l e a d i n g t o agglomeration of p a r t i c l e s and a l s o prevents e a r l y c l o g g i n g o f f i l t e r surface by g e l a t i n o u s d e p o s i t s . Likewise i n j u i c e t o be concentrated, p e c t i n must be removed to avoid f o u l i n g of evapor a t o r s u r f a c e . In these instances i t s absence may be q u a l i t a t i v e l y t e s t e d f o r w i t h a l c o h o l , i n which i t i s i n s o l u b l e . P e c t i n i s n a t u r a l l y degraded during the fermentation of hard c i d e r and wine, r e s u l t i n g i n the d e s i r e d a u t o c l a r i f i c a t i o n . However, p e c t i n i n the appropriate chemical form i s necessary f o r good t e x t u r e of apple pieces and of sauce, p r o v i d i n g the cement t h a t i n s u r e s c e l l cohesion. I t s presence may a l s o reduce the s e p a r a t i o n o f l i q u i d from applesauce. The f i r m i n g of p i e c e t e x t u r e w i t h added calcium i n v o l v e s a b e n e f i c i a l p e c t i c t r a n s formation (16). And, i n the manufacture of j e l l y , p e c t i n may have t o be added to o b t a i n the d e s i r e d g e l s t r e n g t h .



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What i s c e r t a i n from t h i s a n a l y s i s i s t h a t raw product should be s p e c i f i e d and purchased - perhaps even s p e c i a l l y grown - t o s u i t the p a r t i c u l a r needs o f p r o c e s s i n g the intended product. That would be the s h o r t e s t path t o i n s u r e a q u a l i t y product at l e a s t p r o c e s s i n g c o s t . To a l a r g e e x t e n t , and n e c e s s a r i l y , t h i s s e l e c t i o n i s p r a c t i c e d o n l y w i t h the crop or supply a v a i l a b l e at the time o f need. The more c r i t i c a l i s raw product q u a l i t y t o s u c c e s s f u l p r o c e s s i n g , e.g., f o r f r o z e n s l i c e s , t h e g r e a t e r has been the e f f o r t t o meet t h e q u a l i t y requirements by p r e l i m i n a r y c o n t r a c t o r arrangement. Some p r o c e s s i n g p l a n t s are l a r g e enough to process s e v e r a l products having d i f f e r e n t enough requirements to permit best use o f a v a i l a b l e l o t s o f apples. A t y p i c a l example i s the frequent u t i l i z a t i o n o f s m a l l a p p l e s , t h a t can't econom i c a l l y be p e e l e d , i n a j u i c e l i n e along w i t h peel-and-core waste from sauce o r s l i c e p r o c e s s i n g . Although p r a c t i c e d t o some extent by the i n d u s t r y as a whole, the s e l e c t i o n process becomes i n e f f i c i e n t when too many c o n f l i c t i n g and competing decision-makers a c t independently, even though guided by p r i c i n g i n c e n t i v e s . There i s room f o r improvement i n o v e r a l l management o f the crop, and i n t a i l o r i n g f u t u r e s u p p l i e s t o changing needs. T h i s remains an important concern o f the i n d u s t r y .

Literature Cited 1.

Johnson, J. M . , ; Wood, C. B.; Mattus, G. E. V.P.I, & S.U. Ext. Div. Publ. 759. 1977. 2. Anon. IAI Special Letter 1980, 11(9). 3. La Belle, R. L . ; Lind, L. R.; Kime, R. W. Proc. N.Y.S. Hort. Soc. 1978, 123, 180-183. 4. La Belle, R. L. Unpublished data. 1978. 5. Reeve, R. M. Food Res. 1953, 18, 604. 6. Magness, J . R.; Taylor, G. F. U.S.D.A. Circ. 350. 1925. 7. Blanpied, G. D.; Bramlage, W. J.; Dewey, D. H . ; La Belle, R. L . ; Massey, L. M., Jr.; Mattus, G. E.; Stiles, W. C.; Watada, A. E. New York's Food & Life Sci. Bul. No. 74. 1978. 8. La Belle, R. L . ; Shallenberger, R. S.; Way, R. D.; Mattick, L. R.; Moyer, J. C. Food Technol. 1960, 15(9), 463-468. 9. Plane, R. Α.; Mattick, L. R.; Weirs, L. D. Amer. J. Enol. 1980, 31(3), 265-268. 10. Williams, A. A. J . Inst. Brew. (London). 1974, 80, 455. 11. Lea, A. G. H. J . S c i . Food & Agric. 1978, 29, 471-477. 12. Williams, Α. Α.; Lea, A. G. H . ; Timberlake, C. F. In: "Flavor Quality: Objective Measurement". ACS Symposium Series 51. Amer. Chem. Soc., Washington, DC 1977, 71-88. 13. Wilson, D. M.; Nuovo, G. J. J. Appl. Microbiol. 1973, 26, 124-125. 14. Heatherbell, D. A. Alimenta. 1976, 15, 151-154. 15. Van Buren, J. P. Voedingsmiddelentechnol. 1972, 3(13), 67. 16. Collins, J. Ph.D. Thesis. Univ. of Md., College Park. 1966. RECEIVED

April 3, 1981


Quality of Selected Fruits and Vegetables of North America

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