Meat Science 59 (2001) 369–375 www.elsevier.com/locate/meatsci
Quality properties of pork sausage prepared with water-soluble chitosan oligomer C. Joa, J.W. Leea, K.H. Leeb, M.W. Byuna* a
Team for Radiation Food Science and Biotechnology, Korea Atomic Energy Research Institute, PO Box 105, Yusong, Taejon, 305-600, South Korea b Department of Kimchi and Food Science, Chongju National College of Science & Technology, Koesan, Chungbuk, 367-701, South Korea Received 17 January 2001; received in revised form 8 March 2001; accepted 8 March 2001
Abstract Emulsion type sausage was prepared with the addition of a chitosan oligomer (molecular weight 5000, 0.2%) and compared to a control. Sausages were aerobic- or vacuum-packaged and stored in a 4 C refrigerator for 3 weeks. Difference of microbial growth between the sample with added chitosan oligomer or control was not observed (P>0.05). Lipid oxidation was lower in the sausage with chitosan oligomer at 3 weeks in aerobic packaging (P< 0.05) than in the control sausage. The surface color of the sausage with chitosan oligomer had higher Hunter color L*- and b*-value. Hunter color a*-values were lower in the chitosan oligomer-added sausage and the a*-value increased during storage regardless of packaging (P< 0.05). Sensory panels did not detect any difference in color, flavor, texture, and overall acceptance, and mechanical texture analysis also showed no difference. Therefore, the quality of the sausage with added chitosan oligomer (0.2%) was acceptable. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Chitosan oligomer; Sausage; Quality; Storage
1. Introduction Many consumers today use foods as a basic tool for managing their health. A large portion (81%) of consumers selects foods or beverages because they contain healthy ingredients or offer health benefits, such as antioxidant, calcium, or cholesterol-lowering properties (Sloan, 2000). Since chitosan has been reported to have beneficial biological functions such as antimicrobial (Wang, 1992), antitumor (Tsukada et al., 1990), antioxidant (Darmadji & Izumimoto, 1994), and hypocholesterolemic (Razdan & Pettersson, 1994) effects, chitosan and their oligomers (the deacetylated form of chitin) have had great interest in either research or food and pharmaceutical industry. In addition, chitosan and their derivatives have a wide range of unique application potentials including bioconversion of the production of value-added food products (Shahidi & Synowiecki, 1991), recovery of waste material from food processing discards (Bough, 1975), and clarification and deacidification of fruit juice (Imeri & Knorr, 1988). * Corresponding author. Tel.: +82-42-868-8060; fax: +82-42-8688043. E-mail address:
[email protected] (M.W. Byun).
Even though chitin/chitosan derivatives have very strong biological activity, their high molecular weights and high viscosity may restrict their uses (Seo et al., 2000). In addition, because most animal intestines, especially human, do not possess enzymes such as chitinase and chitosanase which directly degrade b-glucosidic linkage in chitin and chitosan and, thus, influences absorption in the intestine (Fukamizo & Brzezinski, 2000). The oligomers of chitin and chitosan have received considerable attention because they may have a greater biological activity than chitosan, and are also water-soluble (Tsigos, Martinou, Kafetzopoulos, & Bouriotis, 2000). Youn, Park, Kim, and Ahn (1999) reported that sausage containing chitosan (0.2%, M.W.=30,000– 120,000) had improved shelf-stability. Sausage made with the molecular weight of 120,000 chitosan completely reduced the microbial levels compared to sausage with NaNO2 added, but the high viscosity of the meat batter created a problem in processing the sausage. Therefore, they recommended the use of the chitosan with the molecular weight of 30,000 or below. Chitosan with a molecular weight of 30,000 is still soluble in only acidic conditions (pH 5.5). Information on the application of chitosan oligomer, however, which may be more functional than chitosan in sausage is still limited.
0309-1740/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(01)00089-4
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The objective of the present study was to determine the effect of water-soluble chitosan oligomer on quality characteristics of cooked pork sausage.
2. Materials and methods 2.1. Sample preparation Vacuum-packaged, refrigerated lean pork and frozen pork backfat, were obtained within 48 h of slaughtering from a local meat packer and ground (Model 160, Fatosa, Barcelona, Spain) twice through a 9-mm and a 3-mm plate, respectively. An emulsion-type pork product was prepared using ground meat, NaCl (1.5% of meat weight), ice water (20%), pork backfat (20%), trisodium phosphate (0.3%), sugar (0.6%), monosodium glutamate (0.03%), sodium nitrite (NaNO2, 156 ppm), and spicemix (0.5%). All ingredients were purchased from Sewoo Co. Ltd. (Seoul, Korea), and the spice mix contained coriander, glucose, red pepper, and onion powder. Chitosan oligomer (0.2%, M.W.=5000, pH=7.2, Shinyoung Chitosan, Co. Ltd, Seoul, Korea) was added to the treated products. Lean pork, salt and phosphate were placed in a silent cutter (C-75, Fatosa, Barcelona, Spain), mixed for about 1 min after which 50% of the ice was added and mixed at high speed. When the temperature of mixture decreased by about 1– 2 C, ground pork backfat was added and mixed until the temperature of mixture reached 10 C. The remainder, 50% of the ice and other spices were added and mixed until the temperature of the mixture reached 13 C. Total emulsification time was about 10 min and processing room temperature was 13 C. The sausages were stuffed (Patron Sausage Filler MWF 591, MADO, Nederland) into a collagen casing (2.5 cm of diameter, Woosung Co. Ltd., Seoul, Korea), dried (45 C for 30 min), smoked (55 C for 40 min) by sawdust, and cooked to 70 C of internal temperature (about 1 h) using a smokehouse (Fracomat 1200, Franke Gm bH & Co., Germany). The cooked sausage was water-spray cooled for 5 min, dried at room temperature for 30 min, and cut into pieces (about 100 g each). Half of the samples were vacuum-packaged (75 cmHg) in oxygen-impermeable nylon bags (2 ml O2/m2/24 h at 0 C; 2030 cm; Sunkyung Co. Ltd, Seoul, Korea) with vacuum packaging machine (Leepack, Hanguk Electronic, Kyungi, Korea) and other half were placed into air flushed bags without sealing. The samples were stored at 4 C until analysis. 2.2. Microbiological evaluation and pH Microbiological evaluation was performed as described by Dymsza et al. (1990) with some modifications. A 10-g sample and 90 ml of sterilized distilled water were
homogenized by a Stomach Lab Blender (Model 400, Tekmar Co., Cincinnati, OH, USA). The homogenate was serially diluted with sterilized distilled water and the diluent was spread on the specific medium in aerobic conditions. Total aerobic bacteria and Enterococci counts were performed with plate count agar (PCA, Difco Laboratories, Detroit, MI, USA) and Enterococcus agar (ENT, Difco). The eosin methylene blue agar (EMB, Difco) was used to grow coliform bacteria. Plates were incubated at 37 C for 72 h and colony forming unit (CFU) per gram were counted, at a dilution giving 30–300 CFU per plate, with Micro Counter (Imaging Products International, Inc., Chantilly, VA, USA). The pH was measured using a pH meter (Model 520A, Orion Research Inc., Boston, USA) by adding 9 parts of deionized distilled water (DDW) into 1 part of sample. 2.3. Lipid oxidation Lipid oxidation was determined as a 2-thiobarbituric acid reactive substances (TBARS) value by using a spectrophotometer (UV 1600 PC, Shimadzu, Tokyo, Japan) as described by Turner et al. (1954). Sausage was homogenized by a Stomach Lab Blender (Model 400, Tekmar Co., Cincinnati, OH, USA) and 0.5 g of sample was added into a 50-ml test tube with 5 ml of 20% trichloroacetic acid (Jusei Chemical Co. Ltd, Tokyo, Japan) in 2 M phosphoric acid (Allied Chemicals Co., Morristown, NJ, USA) and 10 ml of 0.01 M TBA (Sigma Chemical Co., St. Louis, MO, USA). The sample was vortexed and heated in boiling water for 30 min, then chilled in icewater for 10 min. Mixture of isoamylalcohol (Yakuri Pure Chemicals Co., Osaka, Japan) and pyridine (2:1, v/v, 15 ml, Tedia Company Inc, Fairfield, OH, USA) was added to the test tube and vigorously vortexed for 2 min. Then, the sample was centrifuged using a centrifuger (VS-5500, Vision Co. Ltd., Bucheon, Korea) for 15 min at 2400 rpm. The upper layer of the mixture was used for spectorphotometric reading at 538 nm. 2.4. Color measurement Samples were cut into 2-cm thick pieces and measured on the plate of the Color Difference Meter (Spectrophotometer CM-3500d, Minolta Co., Ltd., Osaka, Japan). The instrument was calibrated to standard black and white tiles before analysis. Eight pieces per treatment were evaluated and mean values were used for replication. A medium size aperture was used and the measurement was duplicated. The Hunter color L*-, a*, and b*-values were reported through the computerized system using a Spectra Magic software (version 2.11, Minolta Cyberchrom Inc. Osaka, Japan).
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2.5. Texture profile analysis (TPA)
2.6. Sensory evaluation
The sausage prepared from different treatment combinations was cut into 3-cm thick pieces and placed on the target plate. The two-bite compression test was conducted with a Texture Analyzer (TA-XT2i Texture Analyzer, Stable Micro Systems, Co, England) described by Bourne (1978). The parameters of the program were set at pretest speed 5 mm/s, test speed 5 mm/s, post-test speed 5 mm/s. With a cylindrical probe, 25% of compression was achieved and a texture expert software system (Stable Micro Systems, Co. England) was used to obtain hardness (s), adhesiveness (g s), springness, cohesiveness, gumminess, and chewiness.
The method described by Civille and Szczesniak (1973) was used to evaluate sensory qualities of the sausage. Fifteen semi-trained panelist were used to evaluate products on a 5-point scale: 1, very poor; 2, poor; 3, common; 4, good; 5, very good. The sausage was reheated to a 70 C internal temperature in an oven at 180 C for about 15 min, sliced into 2-cm thick pieces, and served to the panels individually. The sensory parameters used in the present study were flavor, color, texture, and overall acceptance, and were evaluated independently by the panelists three different times.
Table 1 Microbial population changes (CFU/g) of pork sausage prepared with chitosan oligomer in different packaging during storage at 4 C Micro-organisms
Treatment
Packaging
Storage periods (day) 0
Total aerobic bacteria
Control COa
Coliform bacteria
Control CO
Enterobacteriaceae
Control CO
a b
7 5.6105 6.1105 8.0105 1.3105
14
21
1.7107 6.5106 2.1107 2.0107
6.2108 4.1107 7.1108 1.6108
Aerobic Vacuum Aerobic Vacuum
4.1103 1.6103 6.8103 3.0103
Aerobic Vacuum Aerobic Vacuum
NGb NG NG NG
NG NG NG NG
3.5102 1.7102 5.7102 8.7101
4.8103 3.2103 6.2103 2.3103
Aerobic Vacuum Aerobic Vacuum
NG NG NG NG
NG NG NG NG
4.1103 3.3103 7.9102 2.5102
3.6104 2.6104 4.6103 1.5103
CO, Chitosan oligomer (0.2%) added in the product. NG, No growth on plates.
Table 2 The pH of pork sausage prepared with chitosan oligomer in different packaging during storage at 4 Cab Packaging
Treatment
S.E.M.c
Storage period (week) 0
1
2
3
Aerobic
Control COd S.E.M.e
6.44a 6.47a 0.014
6.46aby 6.52ax 0.011
6.39b 6.42b 0.011
6.41ab 6.42c 0.010
0.011 0.013
Vacuum
Control CO S.E.M.
6.47by 6.59x 0.010
6.49by 6.53x 0.007
6.41by 6.51x 0.008
6.53ax 6.41y 0.007
0.012 0.055
a b c d e
Different letters (a–c) within a same row differ significantly (P< 0.05). Different letters (x,y) within a same column differ significantly (P0.05; Table 1). Youn et al. (1999) reported that chitosan oligomers (M.W.=1000 and 5000) did not enhance the preservation effect in sausage. Darmadji and Izumimoto (1994) reported however that, Staphylococci, Coliform, gram-negative bacteria, Micrococci,
Table 3 Absorbance of 2-thiobarbituric acid reactive substances (TBARS) values of pork sausage prepared with chitosan oligomer in different packaging during storage at 4 Cab Packaging
Treatment
S.E.M.c
Storage period (week) 0
1
2
3
Aerobic
Control COd S.E.M.e
0.089b 0.097 0.0110
0.092b 0.076 0.0065
0.112ab 0.105 0.0128
0.142ax 0.090y 0.0065
0.0084 0.0114
Vacuum
Control CO S.E.M.e
0.117 0.110 0.0072
0.120 0.116 0.015
0.120 0.118 0.0122
0.101 0.106 0.0051
0.0075 0.0070
a b c d e
Different letters (a,b) within a same row differ significantly (P< 0.05). Different letters (x,y) within a same column differ significantly (P
