Thermally Generated Flavors - American Chemical Society

Chapter 29

Flavor Properties of Extrusion Cooked Mechanically Deboned Pork Downloaded via TUFTS UNIV on July 10, 2018 at 18:45:57 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Μ. Β. Liu and J. A. Maga Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO 80523

Mechanically deboned pork was blended with varying levels of soy protein concentrate (SPC), non-glutinous rice flour (NGRF) and Chinese five-spice flavor. The mixtures were extruded at 80°-85°C using a single-screw Brabender laboratory extruder equipped with a 3:1 compression screw operating at 100 rpm. Resulting extrudates were air-dried for one hour then soaked in varying concentrations of soy -based marinade at 4°C for 8 hours. Resulting products were then dried at 45°C for two hours. A sensory panel utilized a 9-point hedonic scale to evaluate color, texture, flavor and overall acceptability. Optimum product acceptability resulted with 0.1% added flavoring, 8% SPC and 15% NGRF.

Extrusion technology is a versatile, continuous, high-temperature short-time process that offers new alternatives to conventional food technologies. Foods produced by extrusion have greatly increased in recent years. Based on the attractive characteristics of the extrusion process, food processors have attempted to develop meat-containing products by extrusion cooking (1-2). The potential products include meat analogs, intermediate-moisture meat products and meat-based snacks. Some extrusion systems have been designed to produce meatbased processed foods including skinless sausages; logs of beef, pork, poultry and fish; and dried meat-based products (3-5). In some areas of the world, animal production has been reduced because it is considered a high pollution-producing industry. Meat has become very expensive because of the increasing costs of labor and feeds. Thus, in order to maintain a steady supply of meat at a reasonable price, the greatest concern of the meat industry is to obtain maximum production from each animal. Including the amounts of underutilized edible by-products, any edible meat remaining on the carcass after deboning can be used to accomplish this purpose.

0097-6156/94/0543-0356$06.00/0 © 1994 American Chemical Society

Parliment et al.; Thermally Generated Flavors ACS Symposium Series; American Chemical Society: Washington, DC, 1993.

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The production of mechanically deboned meat (MDM), which can be regarded as a new meat source, is interesting. The world potential production of mechanically deboned pork (MDP) was estimated at 1.9 million metric tons in 1989. Since the carcass weight of pigs is approximately 75% of their live weight and about 83% of the carcass is meat (6), M D P production is equal to about 30 million pigs. These statistics imply that a significant amount of food resources can be saved in the animal industry, and in turn, used for human consumption. Extrusion is capable of producing acceptable texturized meat products by using M D M . Most published reports are centered on mechanically deboned poultry. No reports were found using MDP to produce restructured meat products by extrusion cooking. Other researchers have concluded that non-meat ingredients are required to produce non-expanded moist meat products to improve their texture, binding and flavor. The effects of soy protein products, wheat gluten, gums and starches on the chemical and physical properties have been investigated. However, no applications of rice flour with M D P were found in the literature. Therefore, the overall objective of this study was to develop a non-expanded pork-based product using extrusion processing. Specific objectives include the evaluation of optimum extrusion conditions required to produce the most palatable product texture, optimum non-meat ingredient levels, evaluation of the influence of ingredient mixing order, and the evaluation of texture, color, flavor and overall acceptability of the resulting products. Materials and Methods Materials. Fresh pork bones including the vertebral column and ribs were stored at 18°C. Prior to mechanical deboning, the bones were tempered at 1° to 4°C for 24 hours. Then the bones were ground through a 12 mm plate of a Weiler grinder and deboned using an A U X Beehive mechanical deboner with 0.86 mm holes in the cylinder head. The M D P was mechanically mixed for 3 minutes, vacuum packaged in 2 kg packages and stored at-18°C. The yield of MDP was 34.2%. The proximate composition was 55.6% moisture, 15.3% protein, 25.8% fat and 2.8% ash. Fresh pork back fat containing 9.0% moisture and 89.5% fat at a temperature of -5°C was ground through a 3.2 mm plate twice using a Univex Model PB2 grinder. Before the second grinding, the back fat was frozen to a temperature of -5°C. The finely-ground back fat was then vacuum packed and stored at -18°C. Fat levels evaluated in the formulations were 12, 15, 18, 20 and 21%. The frozen M D P and back fat were thawed to -2° to -5°C prior to being mixed with other ingredients. NGRF was obtained by grinding U.S. #1 California medium grain rice to a particle size distribution of 0.0-2.0, 13.0-19.0, 5.5-9.5, 16.0-22.0 and 16.5-20.5% retained on U.S. sieve # 50, 80, 100, 140, and 200, respectively, and 35.0-41.0% through a U.S. sieve #200. Glutinous rice flour (GRF) was obtained by grinding sweet rice to a particle size distribution of 0.0-1.0, 9.0-15.0, 2.5-8.5, 12.0-18.0 and 12.0-18.0% retained on U.S. sieve #50, 80, 100, 140 and 200, respectively, and 49.055.0% through a U.S. #200 sieve. Initial trials incorporating 0, 15, 17, 20 or 23% of either NGRF or GRF clearly demonstrated that from a textural standpoint, NGRF performed better than GRF and that a level of 15% was the most appropriate. SPC (STA-PRO 3000) was obtained from Central Soya Company. This product is accepted by the USDA for use in meat and poultry products. Initial levels R


358

THERMALLY GENERATED FLAVORS

of SPC evaluated were 0, 5 and 8%, and it was concluded that 8% SPC gave the best textural results. The spice used as a flavoring material was commercial Chinese five-spice powder containing star anise, fagara (wild pepper), cinnamon, cloves and fennel seeds. Initial flavoring levels evaluated were 0, 0.1, 0.4 and 0.7%. Extrusion Cooking. A l l extrusion cooking was accomplished in a laboratory Brabender single screw extruder (Model PL V500) with a 1.92 cm barrel diameter and a 20:1 length-to-diameter ratio. The extruder barrel was equipped with eight 0.79 χ 3.18 mm longitudinal grooves. The desired cooking temperature was controlled by two electrically heated zones, which were in turn controlled by compressed air-cooled barrel collars. Zone one was in the compression section and zone two was in the metering section of the extruder barrel. Samples were prepared 16 hours prior to extrusion cooking. The resulting extrudates were collected and cooled to room temperature and then placed in plastic bags and refrigerated (1° to 4°C) until analyses were performed. Preliminary studies were devoted to the role of zone one/zone two extrusion temperatures on extrudate textural properties. Zone one temperatures evaluated were 80° and 100°C while zone two temperatures evaluated were 80°, 90° and 100°C. It was concluded that a zone one temperature of 80°C and also a zone two temperature of 80°C gave the best results. Extrusion Dies. Three different die configurations were initially evaluated. The first was a flat opening die measuring 6.4 χ 1.5 χ 25.2 mm. The second was a small round die opening measuring 4.6 mm in diameter by 15.8 mm in length, and the third was a large round die that had an opening of 8 mm and was 70 mm long. Compression Screws. Initially both 3:1 and 1:1 compression screws were evaluated, and from these observations it was concluded that the 3:1 screw produced products that had better textural properties than those resulting from the 1:1 screw. The influence of screw speed was also considered, and it was concluded, based on extrudate textural properties, that 100 rpm produced better results than 80 rpm. Ingredient Mixing Order. In an attempt to influence extrudate textural properties, ingredient mixing order was evaluated. In one series of experiments, the NGRF and SPC were first manually dry-blended, then the MDP was added and the complete mixture manually blended for 8 minutes. This was called the rice/soy/pork (RSP) procedure. Another technique evaluated involved first manually mixing the SPC with the M D P for 4 minutes, then adding the NGRF and mixing for an additional 4 minutes (PSR). The last mixing procedure evaluated involved first mixing the NGRF with the M D P for 4 minutes, followed by the addition of the SPC and additional mixing for 4 minutes (PRS). Post-Extrusion Treatments. Several drying techniques were evaluated on the resulting extrudates. In one series, the extrudates were permitted to air dry at room temperature for 24 hours. This was compared to oven drying the extrudates for 2 hours at 45°C.


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Extrusion Cooked Mechanically Dehoned Pork

In another series, the influence of soaking extrudates in two types of marinades was evaluated. The first marinade was called "non-soy" and was composed of 10% sugar and 1% salt in water while the second marinade was composed of 10% soy sauce, 10% sugar and 1% salt, with the remainder being water ("soy"). In both systems, the extrudate was soaked at 4°C for 8 hours, then the extrudate was removed and air dried at 45°C for 2 hours. Sensory Evaluation. The properties of hardness and binding were analyzed using a six-point sensory evaluation method utilizing food references as anchor points (4, 7-8). Six panel members consisting of three males and three females from the Chinese Student Association at Colorado State University were trained to provide scores by comparing the samples used as reference points. The actual foods used are summarized in Table I. For evaluation of extrudate color, texture, flavor and overall acceptability, the same panel used the hedonic scale shown in Table II.

Table I.

Reference Scale for Evaluating Hardness and Binding

1 2 3 4 5 6

Very Soft (Cream Cheese) Soft (Cooked Egg White) Slightly Hard (Frankfurter) Moderately Hard (Olives) Hard (Cheddar Cheese) Very Hard (Peanuts)

Table II.

Raw Ground Beef

Frankfurters Beef Stick

Hedonic Scale Utilized for Sensory Evaluation

Extremely Desirable Very Desirable Moderately Desirable Slightly Desirable Neither Desirable Nor Undesirable Slightly Undesirable Moderately Undesirable Very Undesirable Extremely Undesirable

9

8 7 6 5 4 3 2 1


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Analytical Methods. Standard A O A C (9) methods were used for a duplicate measurement of proximate composition including moisture, protein, fat and ash. Results and Discussion Proximate Composition. For informational purposes, the proximate composition and pH values for the major ingredients utilized in this study are summarized in Table III. Table III. Ingred MDP GRF GRF SPC

2

3

4

1

Proximate Composition (%) Mnisture 55.68 11.44 11.54 6.20

,

PrntPin

15.32 7.00 7.01 69.32 2

and pH of Major Ingredients Eal

àsh

25.83 2.08 2.57 2.15

2.78 1.02 1.01 3.67

pH 6.7 6.3 6.4 6.7

3

MDP=Mechanically Deboned Pork, GRF=Glutinous Rice Flour, NGRF=NonGlutinous Rice Flour, SPC= Soy Protein Concentrate 4

As can be seen, the composition of the two rice flours was essentially the same, and as expected, the SPC was approximately 70% protein. It is interesting to note that the M D P used in this study was close to 26% fat. If M D P was extruded alone, its high fat content would make extrusion difficult due to product slippage in the extruder barrel. Its relatively high fat content is one reason that non-meat ingredients were incorporated. Non-meat ingredients serve two functions. First they dilute the fat content, and secondly, they can tie up a portion of the fat thus minimizing its functional properties. Roles of Rice Type/Amount and Drying on Extrudate Hardness Scores. As can be seen in Figure 1, the type of rice flour utilized had little if any influence on resulting hardness scores. Since NGRF is usually less expensive than GRF, all further studies were conducted with NGRF. As would also be expected, it can be seen that the extrudates that were dried had higher hardness scores than those that were not. Apparently the drying process removed moisture from the system thereby creating a harder product. It can also be seen that increasing the rice flour content from 17 to 23% had little, if any, influence on extrudate hardness. Studies conducted with 15% rice flour displayed similar results, thus further studies were conducted with 15% rice flour since some panel members mentioned detecting a cereal taste in extrudates containing more than 15% rice flour. Sensory Binding Scores as Influenced by Rice Type/Amount and Screw Speed. Sensory binding scores were not dramatically influenced by rice type or the amount of rice used, especially at 17 or 20% rice levels. Binding of product was probably directly related to the degree of starch gelatinization that occurred during the extrusion process, and apparently in this study, similar degrees of gelatinization occurred.


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These data are shown in Figure 2. Also, little influence was evident for extrusion rpm. Hardness and Binding Scores Versus Ingredient Mixing Order. As can be seen in Table IV, the order in which the ingredients were mixed prior to extrusion did influence product textural properties. Dry blending the two powdered ingredients before adding the moist M D P produced the highest hardness score, while mixing the M D P with the rice flour first then adding the SPC, produced the highest bind score. Competition for the moisture in the M D P by the rice flour and SPC probably accounted for these observations. Table Iv. Extrudate Hardness and Binding Scores as Influenced by Ingredient Mixing Order (15% NGRF, 8% SPC, 100 rpm, 80°C) Order

RSP PSR PRS 1

Hardness

1

4.0 3.8 3.9

2

3

2

Rinding

3.2 3.0 3.8

3

RSP=Rice/Soy/Pork, PSR=Pork/Soy/Rice, PRS=Pork/Rice/Soy

Influence of Fat Content. Without question, one would expect that the amount of fat in an extrudate would have a direct influence on its hardness and binding properties. As shown in Figure 3, both of these scores decreased as fat content increased. However, as can be seen, the extrudate containing 12% had hardness and binding scores that were approximately twice that of a product containing 21% fat. From these data it can be concluded that a moderate amount of fat can be incorporated along with non-meat binders to technically produce an extrudate but one must expect rather soft textural properties if this is done. Influence of Spice Levels and Drying. As is apparent in Figure 4, both the amount of added flavoring and the method of drying influenced the sensory properties of the extrudates. In the case of texture, drying actually decreased overall textural properties as compared to nondried samples. The panel felt that the drying process produced an extrudate that was quite hard and thus not acceptable. However, the panel reported that the drying process actually improved extrudate color, flavor and overall acceptability. A flavor addition level in the range from 0.1 to 0.4% gave the most desirable results. Spice Level/Marinade Type. As shown in Figure 5, the use of a soy-based marinade was preferred for overall extrudate acceptability and flavor. However, the type of marinade utilized did not seem to have much effect on extrudate color and texture. Again, an added spice level of 0.1 to 0.4% gave the most desirable results. The naturally-occurring flavor potentiators present in soy sauce probably was responsible for improving overall extrudate acceptability.


362


HINGRF •GRF

17

20

23

UNTREATED

17

20

% RICE

23

DRIED

Figure 1. Extrudate hardness scores as influenced by rice type/amount and drying (100 rpm, 80°C).

17

20 80 RPM

23

17 %RICE

20

23

100 RPM

Figure 2. Extrudate binding scores as influenced by rice type/amount and screw speed (80°C).


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6

% FAT

Figure 3. Extrudate hardness and binding scores as influenced by fat content (15% NGRF, 8% SPC, 100 rpm, 80°C).

•0.0 % SPICE UJ GC Ο Ο CO

mo.1%

SPICE

M0A%

SPICE

fflO.7% SPICE

FLAVOR

Figure 4.

OVERALL

Extrudate panel scores as influenced by spice level and drying.


364


•0.0% SPICE EU0.1% SPICE rao.4%spicE BB0.7% SPICE

COLOR

TEXTURE

FLAVOR

OVERALL

Figure 5. Extrudate panel scores as influenced by spice level/marinade type (15% NGRF, 8% SPC, 100 rpm, 80°C).

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9.

Linko, P. Res. Food Sci. Nutr.1983, 5, 365-375. Harper, J. M. Food Technol. 1986, 40 (3), 70-76. Smith, Ο. B. Cereal Foods World 1979, 24, 132-133, 135. Ba-Jaber, A. S. Ph.D Thesis, Colorado State University, Fort Collins, 1990. Alvarez, V. B.; Smith, D. M.; Morgan, R. C.; Booren, A. M. J. Food Sci. 1990, 55, 942-946. Lawrie, R. W. Meat Science; Pergamon Press: New York, 1985. Szczesniak, A. S.; Brandt, Μ. Α.: Friedman, J. J. Food Sci. 1963, 28, 397-403. Clarke, A. D.; Sofos, J. N.: Schmidt, G. R. J. Food Sci. 1988, 53, 711-726. AOAC, Official Methods of Analysis, 14th Ed. Association of Official Analytical Chemists: Washington, DC, 1984.

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13, 1993


Thermally Generated Flavors - American Chemical Society

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