Protein-Generated Extrusion Flavors - American Chemical Society

Chapter 46

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on April 14, 2016 | http://pubs.acs.org Publication Date: October 3, 1989 | doi: 10.1021/bk-1989-0409.ch046

Protein-Generated Extrusion Flavors Joseph A. Maga and Chin Hong Kim Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO 80523

Varying amounts of defatted soy flour (DSF), soy protein concentrate (SPC) sodium caseinate (SC), whey protein concentrate (WPC), and gluten (G) (0-50%) were added to corn starch and adjusted to either 15 or 25% moisture. The blends were extruded at either 120 or 150°C dough temperature in a Brabender laboratory extruder. Volatiles were recovered from resulting extrudates and analyzed by gas chromatography. Sensory evaluations of blandness were compared with the instrumental results. A greater number of volatiles and/or higher relative concentrations were observed with increasing protein levels. DSF produced the greatest number of detectable peaks while SPC had the least. Low temperature and high moisture extru sion conditions resulted in the most peaks, while high temperature and high moisture yielded the least. Sensory blandness scores magnified with increasing temperature and decreasing moisture. The extruder is a continuous high-temperature short-time reactor. Ingredients, moisture, temperature, pressure, and shear can i n t e r a c t i v e l y produce many Maillard-type flavor compounds. As the extrudate exits the extruder, many of the v o l a t i l e reaction products may be lost with steam since the extrudate passes from a zone of r e l a t i v e l y high pressure within the extruder to atmospheric pressure. By c o n t r o l l i n g formulation variables, the extruder can serve as a useful tool to thermally produce v o l a t i l e and nonvolatile compounds which make s i g n i f i c a n t contributions to overall f l a v o r . H i s t o r i c a l l y , most extrusion processors have r e l i e d on postextrusion flavor application as a means of c h a r a c t e r i s t i c a l l y 0097-6156/89/0409-0494$06.00/0 ο 1989 American Chemical Society Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


46. MAGA AND KIM

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flavoring t h e i r products. This is not ideal in most situations due to cost, flavor usage levels required, and additional steps in processing. During extrusion, general browning t y p i f i e d by caramelization, M a i l l a r d , and oxidative decomposition reactions are paramount in flavor compound formation. Temperature and shear conditions occurring during extrusion can provide the chemical and physical means whereby complex starch and protein can be p a r t i a l l y degraded to provide reactants that can then p a r t i c i p a t e in browning. Browning reactions usually produce product darkening. However, from a flavor generation standpoint, browning is usually a highly desirable reaction during extrusion. Therefore, formulations and operations in most cases should be optimized to take advantage of browning. In the case of caramelization, a simple sugar such as glucose, can produce a wide variety of f l a v o r f u l heterocyclic compounds. Glucose can be added or formed during extrusion via starch degradation, e n o l i z a t i o n , dehydration, and c y c l i z a t i o n . It is interesting to note that fructose is generally considered to be more thermally reactive than glucose. However, i t has been reported that glucose is more active than fructose during extrusion (1). By thermal and shear forces during extrusion which cause protein rearrangement/degradation, the Maillard reaction progresses, and a wide variety of potent flavoring compounds can result. Reaction rates in turn are influenced by the types of sugars and amino acids present, temperature, water a c t i v i t y , duration of heating, and pH. Published studies on extrusion formation/retention of f l a v o r are rather limited ( Î L 8 ) . None have reported the e f f e c t s of protein sources and concentrations on flavor compound formation in extrudates, the major objective of this study. Materials and Methods Ingredients. A l l ingredients were obtained commercially along with compositional information and consisted of corn starch (National Starch, Bridgewater, NJ), whey protein concentrate (WPC) and sodium caseinate (SC) (Leprino Foods, Denver, CO), defatted soy f l o u r (DSF) (Archer Daniels Midland, Decatur, IL), soy protein concentrate (SPC) (Central Soya Company, Fort Wayne, IN), and gluten (G) (Ogilvie M i l l s L t d . , Montreal, Canada). Pre-Extrusion Blending. Based on the moisture contents of the corn starch and various protein sources, blends of 0,5,15,30, and 50% (dry weight) of each protein source were made by f i r s t dry mixing for 10 minutes in a Paterson-Kelly Model LB-P-8 twin shell blender followed by the appropriate amount of 20°C tap water to obtain a total moisture content of either 15 or 25% (wet b a s i s ) . The moistened mixtures were then blended for an additional 20 minutes followed by overnight e q u i l i b r a t i o n at room temperature in a i r - t i g h t bags.

Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

THERMAL GENERATION OF AROMAS


496

Extrusion. A Brabender PI asti corder Extruder Model PL-V500 with a 19.05 mm barrel diameter, a 20:1 barrel length to diameter r a t i o , eight 0.29 χ 3.18 mm longitudinal grooves and a die plate equipped with a 4.75 mm diameter by 1.27 cm length die was used. The unit was equipped with a variable speed drive which was set at 120 rpm for a l l runs. The barrel was equipped with two e l e c t r i c a l l y heated, compressed a i r cooled c o l l a r s controlled by thermostats. Nonisothermal temperature conditions were used with increasing temperature toward the d i e . A thermocouple placed in the dough stream just before the dough exited the die as extrudate was used to measure dough temperatures of 120 and 150°C. A 3/1 compression screw r a t i o was used for a l l runs. A l l formulation and extruder variables/conditions are summarized in Table 1. Table I.

Formulation and Extruder Variables

Variable Protein type WPC, SC, DSF, SPC, G Protein level Feed moisture Dough temperature Screw configuration-speed Die size

Evaluated

Level 0,5,15,30,50% 15,25% 120, 150°C Constant (3:1, 120 rpm) Constant (4.75 mm)

Samples from each variable were collected and permitted to a i r dry overnight and then milled to pass through a 1 mm screen. Extraction and Concentration. Five 5-gram units of each ground extrudate were placed into f i v e micro-Kjeldahl f l a s k s . F i f t y ml of 80°C deionized water were added to each f l a s k , the flask connected to the d i s t i l l a t i o n apparatus and 40 ml of d i s t i l l a t e collected in a screwcap test tube. Eight ml of freshly r e d i s t i l l e d diethyl ether were added to each 40 ml of d i s t i l l a t e and shaken vigorously for 30 seconds. The ether layers from the f i v e d i s t i l l a t e s were combined and cooled in dry i c e . Therefore, a total of 25g of each extrudate was extracted. The ether extracts were then concentrated down to approximately 3 ml and transferred to a 5 ml graduated micro v i a l . The sample was further concentrated to 0.3 ml in a dry ice bath using nitrogen and stored on dry ice u n t i l analyzed. Gas Chromatographic Analysis. A Hewlett Packard Model 5830A gas chromatograph equipped with a Model 18850A data terminal was used. The column was 1/8" by 10' stainless steel packed with 10% Carbowax 20 M on 100/120 mesh Gaschrom P. An i n i t i a l oven temperature of 100°C was held for 3 minutes after injection and then increased at a rate of 2°C/minute to 207°C and held for another 65 minutes. Injection and detector temperatures were 225°C and nitrogen at a flow rate of 26 cc per minute. Typical separations are shown in Figure 1. Sensory Evaluation: Two expert sensory evaluation members within the Department were asked to rate the blandness of each extrudate




46. MAGAANDKIM


497

498


using a 10-point scale with 1 being bland and 10 strong. were provided for them to taste along with rinse water.

Samples

Results and Discussion:


Sensory Blandness. The sensory blandness summarized in Table II.

for a l l treatments

is

Table II.

Sensory Blandness

Scores

% Protein 5 15 30 50

Conditions LTLM

DSF 1 3 3 4

SPC 2 4 6 7

WPC 4 5 6 7

SC 2 6 6 8

G 2 3 3 4

Control 1

5 15 30 50

LTHM

1 2 3 5

2 3 3 5

2 3 4 6

3 4 6 7

2 2 3 4

1

5 15 30 50

HTLM

4 5 6 8

5 7 7 9

3 4 6 9

4 6 8 9

5 6 6 8

3

5 15 30 50

HTHM

3 4 6 8

3 3 6 7

3 4 7 8

4 5 7 8

3 5 6 7

2

LTLM: Low temperature low moisture; LTHM: Low temperature high moisture; HTLM: High temperature low moisture; HTHM: High temperature high moisture. 1 = Bland; 10 = Strong As can be seen, as protein concentration increased, blandness decreased. Overall i t was concluded that DSF and G were the blandest protein sources evaluated while SC was the least bland. Perhaps the differences in protein contents within the same series (DSF and SPC; WPC and SC) produced these observed d i f f e r e n c e s . It was also apparent that the two high temperature sets of samples were not as bland as the low temperature s e r i e s . Within each set, high moisture produced blander tasting products than low moisture. More f l a v o r f u l compounds were produced with high temperature, apparently due to thermal decomposition reactions. Perhaps, high moisture produced starch/protein structures do not permit the rapid and/or complete release of flavor compounds in the mouth. GC V o l a t i l e Comparison. It can be seen from Table III that certain v o l a t i l e s were only observed in s p e c i f i c protein sources. For example, Peak 2 was only present in milk protein sources (WPC and SC) while Peak 3 was evident in soy protein sources (DSF and


46. MAGAANDKIM


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SPC) and the control starch extrudates. Peaks 31, 33 and 35 appeared to be unique to G. On the other hand, some peaks (23, 38, 42-46) were found in a l l products including the starch control indicating that they were starch derived. It can also be seen that DSF had the most observed peaks while SPC had the l e a s t . Perhaps nonprotein components associated with DSF also thermally reacted to form detectable components. When v o l a t i l e data are compared to sensory blandness scores as discussed above, i t becomes apparent that the measurements do not t o t a l l y agree. DSF was subjectively evaluated as being rather bland in taste while SPC was stronger. In contrast the objective gas chromatographic data would indicate otherwise. In a l l p r o b a b i l i t y , certain v o l a t i l e compounds in SPC at higher levels than DSF (Peaks 7, 18, 20, 23, 24) are responsible for these differences. With the two milk protein sources (WPC and SC), one would have predicted from a thermal standpoint that WPC should have provided more v o l a t i l e s than SC because i t is a source of highly reactive carbohydrates. From Table III, i t can be seen that this was not the case. However, only residual v o l a t i l e s were evaluated and i t is pausible that SC had retained more v o l a t i l e s than WPC due to i t s higher protein content. When extrusion conditions are considered (Table IV), the most severe conditions (HTLM) resulted in the loss or decreased level of certain peaks; however, the remaining components were at r e l a t i v e l y high l e v e l s . The least severe conditions (LTHM) retained the highest number of v o l a t i l e s . Also, certain peaks were associated with high moisture conditions but were not apparent in low moisture conditions, while other peaks were only observed at low temperature conditions. Relative peak concentration for some v o l a t i l e components increased during severe conditions indicating t h e i r thermal formation and retention. From Table V, which represents increasing levels of SPC, i t can be seen that some components were at the same r e l a t i v e concentration throughout, while others magnified. Perhaps variations in water a c t i v i t y and/or shear conditions within the extruder can p a r t i a l l y explain some of these differences. Conclusions This i n i t i a l study c l e a r l y demonstrated that protein type and amount as well as extrusion conditions can result in a vast array of both sensory and v o l a t i l e compound differences. Further research, including compound i d e n t i f i c a t i o n , is required to more f u l l y understand the complex interactions observed.


500

THERMAL GENERATION OF AROMAS Table III.

Gas Chromatographic V o l a t i l e Comparison, Extrusion Conditions: HTLM


Protein Sources (50%) Peak No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 + ++ +++

SPC

WPC

SÇ

G

Con

+++ +++ +++

+++

+++

+++

++ +

-

+++ +++

+++ ++ + -

DSF

+++ ++ -

+++ + + + ++ -

+++ ++ +++ ++ ++ ++ ++ ++ ++ +++ ++ ++ +++ ++ ++ + ++ ++ +++ + + + +++ +++ +++ +++ +++

-

-

-

-

++

++ -

-

+ -

++ -

+++ +++ ++ -

+++ +++ ++ -

++ -

+++

+++ +++ +++ ++ ++

-

-

+ + ++ -

+ + + ++ -

++ ++ -

-

+ +++ + ++ +++ +++ ++ ++

-

+++ ++ + -

+ +++ ++ -

+ ++ ++ ++ + ++ ++ ++ -

+ + ++ ++ -

++ + + +++ + +++ ++ ++ ++

-

+++ -

++ ++ -

+ + + ++ -

++ ++ ++ -

++ ++ ++ -

-

++ + -

-

-

+ -

-

++ -

-

-

-

-

+ -

+++ -

+++ -

-

+++ -

+

-

-

+ ++ ++ ++ ++

++ +++ ++ ++ ++

100,000


46.

MAGA AND KIM

501


Table IV.

Gas Chromatographic V o l a t i l e Comparison


SPC (50%) Peak No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

HTLM

+++ +++ +++ -

++ -

+ ++ +++ +++ ++ -

+++ +++ ++ ++ -

++ -

+ ++ ++ ++

Extrusion Conditions: HTHM LTLM

+++ ++ + + + + + -

++ ++ ++ ++ + +++ ++ ++

++ ++ + +++ + + ++ ++ + + ++ ++ + ++ -

+ + + + +++ + ++ ++ ++ ++ ++


LTHM

+++ ++ + ++ + +++ + + ++ ++ ++ +++ ++ + ++ ++ ++ + ++ ++ + + ++ ++ ++ ++ ++ ++ +++ ++ +++ +++ +++ +++ +++


502


Table V. Gas Chromotographic V o l a t i l e Comparison, Extrusion Conditions: HTLM Peak No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

0

++ + ++ ++ + -

++ -

+++ ++ ++ +++ ++

5

+++ ++ ++ + ++ + + ++ ++ ++ + + ++ ++ ++ +++ + + ++ ++ +++ ++

SPC level 15

+++ ++ ++ ++ + + ++ ++ -

++ + +++ ++ ++ ++ +++ + ++ +++ +++ ++

(%)

50

30

+++ +++ ++ ++ ++ -

+ + ++ ++ ++ ++ ++ + + + +++ + ++ +++ +++ +


-

+++ +++ +++ ++ -

++ -

++ ++ +++ +++ ++ +++ +++ ++ ++ -

+++ + -

++ +++ +++ +

46. MAGA AND KIM



Literature Cited 1. Li Sai Fong, J.C. Ph.D. Thesis, University of Montpellier, France, 1978. 2. Blanchfield, J.R.; Ovenden, C. Food Manufact. 1974, 49(1), 2728,51. 3. Chen, J.; Reineccius, G.A.; Labuza, T.P. J Food Technol. 1986, 21, 365-383. 4. Delache, R. Getreide. Mehl Brot 1982, 36, 246-248. 5. Lane, R.P. Cereal Foods World 1983, 28, 181-183. 6. Lazarus, C.R.; Renz, K.H. Cereal Foods World 1985, 30, 319320. 7. Kim, C.H.; Maga, J.A. Lebensm. Wiss. Technol. 1987, 20, 311318 8. Palkert, P.E.; Fagerson, I.S. J. Food Sci. 1980, 45, 526-533. RECEIVED

July 6, 1989


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Protein-Generated Extrusion Flavors - American Chemical Society

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