CHARACTERISTICS OF MINCED BEEF STORED AT CHILLED AND ABUSE TEMPERATURES

Fresh minced beef samples were collected from retail food stores in the Eastern United States and stored for various periods at 4 and 25C. Evaluations included psychrotophic counts, microbial taxonomy, pH, total volatile nitrogen, malonaldehyde (TBARS), color and off odor. Minimal discoloration was observed through 5 days of storage at 4C; whereas, minced beef stored at 25C sustained major discoloration prior to storage for 12 h. After five days of storage at 4C, 11.6% of the samples exhibited an off odor compared to 29.8% after storage for 12 h at 25C. Psychrotrophic counts of less than 10⁵/g were attained during storage at 4C for 5 days; whereas, samples stored at 25C exceeded this level after 12 h. Chemical indices suggested similar product deterioration. These observations suggested that fresh minced and aerobically packaged in a 4C environment will attain acceptable color without off odor development through 5 days of storage.     

EFFECT OF GAMMA IRRADIATION ON AFLATOXIN B1 PRODUCTION BY ASPERGILLUS FLAVUS IN GROUND BEEF STORED AT 5C

The effect of γ-irradiation for controlling the production of aflatoxin B₁ by Aspergillus flavus in ground beef stored at 5C for 2 weeks was investigated. Aspergillus, Penicillium, Cladosporium, Mucor, Scopulariopsis, Candida and Rhodotorula were the most common fungal genera contaminating ground beef. A. flavus and A. niger were the most common Aspergillus spp. Aspergillus flavus isolates were able to produce aflatoxin B₁ in ground beef. Only 3 (20%) samples of ground beef were contaminated with aflatoxin B₁ (25–45 μg/Kg). Gamma irradiation dose levels resulted in an immediate reduction in the total numbers of A. flavus. No growth or aflatoxin B₁ production occurred at 1.50 kGy during storage.     

EFFECT OF SPICES ON GROWTH AND SURVIVAL OF SALMONELLA TYPHIMURIUM DT 104 IN GROUND BEEF STORED AT 4 AND 8C

Few studies have addressed the use of spices against pathogens associated with meat. The effects of garlic, ginger and turmeric were evaluated against Salmonella Typhimurium DT 104 that were inoculated either in spice paste or in buffered peptone water (BPW) or in heat‐treated ground beef and stored at 4 and 8C for 10 days. Data from the spice pastes study showed a decrease in Salmonella Typhimurium DT 104 counts, and the greatest reduction (3.39 log) was observed in garlic paste stored at 4C. Garlic in BPW data showed a reduction of 1.5 and 1.0 log in Salmonella Typhimurium counts at 4 and 8C, respectively. Ground beef stored at 4C showed no growth or a slight reduction in growth in samples with spice, while all samples at 8C showed an increase in Salmonella Typhimurium counts. Results show that the spices inhibit or inactivate Salmonella Typhimurium DT 104 when they are in direct contact. However, when spices are added to a complex food system such as ground beef, the inhibitory activity of these spices considerably decreases.     

CHANGES IN BIOGENIC AMINE CONTENTS AND SENSORY QUALITY OF SARDINE (SARDINA PILCHARDUS) STORED AT 4C AND 20C

Biogenic amines (tyramine, putrescine, cadaverine, histamine, spermidine and spermine) in sardine during the storage at two temperatures (4C and 20C) were investigated. Changes in sensory scores were also recorded. Significant differences between storage times were found. The levels of tyramine, putrescine, cadaverine and histamine increased as decomposition of sardine progressed at both 4C and 20C. Spermidine and spermine did not change throughout storage. Putrescine was the main biogenic amine formed, followed by tyramine, cadaverine and histamine. Histamine remained lower than the toxic level of 100 mg/kg in the samples stored at 4C whereas it exceeded the toxic level after 16 h at 20C. The increase in histamine concentration was lower than tyramine and putrescine at both temperatures. Sensory scores gradually decreased during the storage.     

POSTMORTEM BIOCHEMICAL AND TEXTURAL CHANGES IN THE ADDUCTOR MUSCLE OF CATARINA SCALLOP STORED AT 0C

Postmortem characteristics of the adductor muscle of the Catarina scallop were evaluated for biochemical, chemical and textural changes during a 15‐day storage period in ice (0C). K‐value, pH, nitrogen of trimethylamine (TMA‐N), nitrogen of total volatile bases (TVB‐N), water‐holding capacity (WHC), color and texture changes were monitored. K value increased linearly from an initial value of 20.5 to 68.5% at day 15. Spoilage indicators TVB‐N and TMA‐N (mg/100 g) increased from 13.5 and 2.6 to 21.4 and 3.4, respectively. However, they remained below critical limits, suggesting low microbial activity. In contrast, texture, pH, WHC, and color were not affected. Overall results indicated that the quality of iced Catarina scallop adductor muscle packed in ice was maintained over a period of 15 days.     

BACTERIA-INDUCED BIOCHEMICAL CHANGES IN CHICKEN SKIN STORED AT 5°C

SUMMARY: The effect of psychrotolerant bacteria on the water-holding capacity as measured by the extract release volume (ERV), pH and protein degradation in chicken skin stored at 5°C was determined using strains of Achromobacter and pigmented and nonpigmented Pseudomonas. All organisms caused a rapid decrease in ERV to about 50% of the original value during the early log phase of growth before development of off-odor. Changes in pH and content of extractable nitrogenous materials occurred during bacterial growth but were not pronounced until after the count was greater than 10⁸ cells/g of skin and a faint off-odor was detectable. The content of extractable materials decreased during the early log phase, corresponding to the period of rapid increase in pH; later, during the late log or stationary phases of growth, it rapidly or gradually increased, depending on the organism.     

MUSCLE CATHEPSINS IN THREE SPECIES OF PACIFIC SOLE

The cathepsins in saline muscle extracts of three species of Pacific sole were investigated. A buffered hemoglobin solution (pH 3.0) served as substrate for the enzyme assay. No apparent change in catheptic activity in muscle homogenates of English sole was observed during 25 days of frozen (−26 °C) storage. Partial characterization of the cathepsins indicated a pH activity optimum of 3.0–3.5 for rex and petrale sole but a slightly higher PH optimum of 3.2–3.8 for English sole. The three species showed a temperature optimum of 45 °C for hemoglobin splitting. A wide variation in catheptic activity within the species was observed for rex sole while English and petrale sole showed more uniform catheptic activity. The mean activities for the three species varied significantly (P < 0.05). Results of sensory evaluation of muscles containing high and low levels of catheptic activity from the three species of sole did not support the assumption that cathepsins have a substantial influence upon the quality of marine food fish.     

EFFECT OF SOLUBLE SOLIDS AND TEMPERATURE ON ASCORBIC ACID DEGRADATION IN LEMON JUICE STORED IN GLASS BOTTLES

Lemon juice at concentrations of 9°, 20°, 30°, 40° and 50°Brix was stored at 10°, 20° and 36°C for 16 weeks and sampled regularly for total soluble solids (TSS), pH, titratable acidity and ascorbic acid. No significant differences were found in the first two of these factors as a function of storage time. There was a small but significant decrease in citric acid concentration over 16 weeks. Ascorbic acid loss was greater at higher temperatures; at a constant temperature, the loss was smaller as TSS increased. Ascorbic acid degradation data fitted zero-, first- and second-order models equally well at all five TSS. Rate constants in 9°Brix juice were significantly higher than those for the other four concentrations at all three temperatures. E_a values of 47.8 and 24.1 kJ mol^?1 were calculated for ascorbic acid degradation in 9° and 20°Brix juices. The effect of temperature far outweighed the effect of TSS on ascorbic acid degradation. Over the 16-week storage period, maximum retention of ascorbic acid (95.7%) was obtained in the 50°Brix lemon juice concentrate stored at 10°C.     

THE DEGRADATION OF MYOFIBRILLAR PROTEINS IN BEEF AND LAMB USING DENATURING ELECTROPHORESIS - AN OVERVIEW

Degradation of specific myofibrillar proteins has been followed in many studies using SDS-PAGE (denaturing) electrophoresis and these have shown that proteins such as titin, nebulin, troponin-T, desmin, filamin and vinculin are degraded at different rates during postmortem storage of meat. Although informative, electrophoresis is usually restricted to qualitative interpretation of the gels and there have been few studies that have quantitatively linked the degradation of specific proteins to changes in toughness. Improved quantitative methods (including scanning densitometry, image analysis, and modeling approaches) will be necessary to determine the protein and/or protein alterations that cause postmortem tenderization. This approach is complementary to other measurements of proteolysis where the objective is to more adequately explain the variation in toughness.     

MATHEMATICAL MODELING OF MICROBIAL GROWTH IN FRESH FILLED PASTA STORED AT DIFFERENT TEMPERATURES

Growth curves for a selection of pertinent microorganisms in ricotta and ricotta-filled ravioli were analyzed in terms of Gompertz's model. The growth of Enterobacteriaceae, molds and yeasts and psychrotrophic microorganisms during storage at 0, 4, 8 and 10C was determined. Lag phase duration and specific growth rate were inversely related. The activation energies from an Arrhenius-type equation were calculated for the microorganisms under study. For ricotta samples, molds and yeasts were the most sensitive organisms showing E_μ values of 74.60 KJoule/mol while Enterobacteriaceae and psychrotrophic microorganisms had E_μ values of 24.30 and 25.70 KJoule/mol, respectively. For ricotta-filled ravioli samples, the three microorganisms showed activation energies in the range of 31.47–32.99 KJoule/mol; hence the temperature dependence of their growth rates was comparable. Results allow to predict microbial growth of different microorganisms in ricotta and ricotta-filled ravioli when exposed to different storage temperatures.