EXPOSURE TIME ON BACTERIA FLORA/COUNT AND SHELF LIFE OF CANNED SARDINE (SARDINELLA PILCHARDUS) UNDER AMBIENT AND COLD STORAGE CONDITIONS

This study is aimed at investigating the exposure time on bacteria flora/count and shelf life of conned sardine (Sardinella pilchardus) under ambient and cold storage conditions. Twenty‐five cans with an average weight of 165.05 g of the Titus (with an expiration date of 4 years (September 30, 2004 to September 30, 2008 of batch no. 1432) were purchased and stored at the ambient temperature of 27C and cold (?4C) storage conditions as samples for 12 weeks (precisely between June 15 and September 10, 2005 when the experiment lasted). Proximate analysis of the samples was taken at the beginning of the experiment and at the end for both the ambient and cold stored (after an exposure time of 24 h). Initial baseline and biweekly studies were carried out for 12 weeks for: (1) organoleptic (odor, taste, texture, appearance, rigidity of flesh, color and reaction of fish with can); (2) chemical (trimethylamine [TMA], peroxide values [PVs] and thiobarbituric acid [TBA]); and lastly (3) microbiological analysis for bacteria count and identification of the bacteria on the samples from each storage environment after an exposure time of 24 h in each case. All the chemical parameters (TMA, TBA and PV) were significantly (P < 0.05) correlated with exposure/storage time. Correlation coefficients r = 0.60, 0.66 and 0.54 were low in all classes therefore indicating spoilage rate increases slightly with exposure time/storage period. The highest PV (0.023–0.715), TBA (0.057–1.056) and TMA (1.01 × 10³–3.63 × 10³) ranges were recorded for canned sardines stored at ambient temperature of 27C. However, these are still within acceptable tolerance limit (i.e., organoleptic score of 4–7). Organoleptic assessment with average scores of 5.5 and 6.0 was recorded for cold and ambient stored samples. No viable bacteria count was recorded for cold‐stored samples throughout the experiment. However, the range initial 1.0 × 10⁵ and final 5.0 × 10⁴ cfu/g total plate counts recorded for ambient storage were still below the minimum bacteria count for spoilage that could cause significant or deleterious effect that could result in food poisoning. Traces of the following bacterial species were recorded at ambient temperatures: (1) Bacillus subtilis (1.2 × 10⁴ cfu/g); (2) Streptococcus faecium (9.0 × 10³ cfu/g); (3) Proteus vulgaricus (7.0 × 10⁵ cfu/g); (4) Pediococcus halophilus (6.0 × 10⁵ cfu/g); (5) Micrococcus acidophilus (4.0 × 10³ cfu/g); (6) Streptococcus lactis (4.0 × 10³ cfu/g); and (7) Aerobacter aerogenes (4.0 × 10³ cfu/g), while fungal species Aspergillus terreus (1.0 × 10³ cfu/g) and Aspergillus niger (3.0 × 10³ cfu/g) were recorded also for samples stored at ambient temperature of 27C. Hence, in view of this, the 4‐year recommended expiration date may be upheld for canned sardine (S. pilchardus fish products in oil sources) provided the hazard analysis and critical control points, and closely monitored. It is, therefore, recommended that exposure of canned sardine in oil should not exceed 12–24 h under whatever food storage temperatures to avoid food poisoning.     

不同添加剂对鸡腿肉盐溶蛋白热诱导凝胶保水性的影响

以鸡腿肉为原料,研究不同添加剂对鸡肉盐溶蛋白热诱导凝胶保水性的影响.从鸡腿肉中提取盐溶蛋白,再向盐溶蛋白溶液中分别添加大豆分离蛋白(3%、5%、7%、9%、11%)、卡拉胶(0.1%、0.3%、0.5%、0.7%、0.9%)、花生蛋白(3%、5%、7%、9%、11%),再分别在40℃～90℃加热.形成热诱导凝胶,用离心法测定其凝胶的保水性.结果表明,当大豆分离蛋白、卡拉胶、花生蛋白单独分别添加浓度为7%、0.5%、7%,加热温度分别为80、70、80℃时,凝胶的保水性达到最佳.     

EFFECT OF ENZYMATIC HYDROLYSIS ON SOME FUNCTIONAL PROPERTIES OF WHEY PROTEIN

A study was undertaken to further elucidate the functional properties of whey protein with respect to foaming and emulsifying capacities and to observe the effect of enzymatic hydrolysis on these properties. Emulsion capacity decreased as proteolysis continued suggesting there is an optimum mean molecular size of the proteins involved which is lower than that of casein. Heat treatment of the reconstituted protein concentrate was necessary for foam stability; specific volume and foam stability increased directly with temperature of heating. Re effect of pH on whippability, data indicate that the greater the net charge the greater the tendency to foam. A limited amount of hydrolysis appears desirable to increase foaming but greatly decreases foam stability.     

EFFECT OF RADURIZATION ON SHEAR RESISTANCE AND FRAGMENTATION OF CHICKEN MUSCLE

SUMMARY —Excised pectoralis muscles of chicken received radurizing doses of γ-radiation at varying times post-mortem to determine the effect on shear resistance, myofibrillar fragmentation (F-ratio) and pH. Irradiation doses between 0.1 and 0.3 Mrad produced decreases in F-ratio and increases in shear resistance. The magnitude of the changes was directly proportional to the duration of postmortem aging prior to irradiation. Muscle pH subsequent to irradiation between 2 and 12 hr post-mortem was not significantly affected by any of the dose-time treatment combinations. Shear resistance and F-ratio changes were strongly correlated on an average basis (r =+ .857; n = 6) but not on an individual sample basis.     

EFFECT OF FREEZING AND PACKAGING METHODS ON SURVIVAL AND BIOCHEMICAL ACTIVITY OF SPOILAGE ORGANISMS ON CHICKEN

SUMMARY— A study was conducted to determine effects of freezing, thawing, and subsequent holding at about 5°C on survival or growth of aerobic bacteria on chicken packaged with various materials. Production of fluorescent pigment, and extracellular proteinase and lipase activities were used as indices of the ability of the organisms to produce spoilage. Growth of bacteria was determined by colony counts. Assays for proteolysis were made by means of a dye binding method; lipolysis of chicken fat was determined by titration of free fatty acids. Fluorescent pigment formation was evaluated by means of a photofluorometer. The influence of availability of oxygen on proteolytic and lipoytic spoilage of poultry was studied after chicken was packaged with materials having high or low oxygen permeability and by vacuum packaging. Fluorescent pigment production, proteofytic and lipolytic spoilage of chicken stored at 5°C was directly related to the availability of oxygen provided by the packaging procedure. Bacterial numbers paralleled increases in biochemical indices of deterioration. Freezing of chicken at −29°C for 35 days followed by defrosting and refrigerated storage increased the proportion of biochemically active psychrophiles on the surface of the meat. Vacuum packaging generally limited amount of spoilage as measured by the criteria specified. When samples were analyzed after alternate freezing and thawing, total aerobic bacterial counts were only slightly different from those on chicken frozen continuously for 22-25 days.     

TRIALS ON THE ANTIBACTERIAL EFFECT OF GLUCOSE OXIDASE ON CHICKEN BREAST SKIN AND MUSCLE

Use of glucose oxidase as a possible means to inhibit microbial growth on processed poultry was evaluated. Muscle and skin sections of chicken breast were inoculated with Pseudomonas spp. or Salmonella typhimurium and subjected to either: (1) 60 s dip in 2 units of glucose oxidase without glucose supplementation or (2) 60 s dip in 2 units of glucose oxidase with 4% glucose supplementation. Control groups were dipped in sterilized, distilled water. The Pseudomonas and Salmonella populations were determined for each section. Neither enzyme treatment reduced the initial Pseudomonas or Salmonella populations nor did the treatments inhibit the growth of Pseudomonas during the storage period . Salmonella was inhibited by the low temperature. Therefore, a glucose oxidase enzyme treatment has little potential for extending the shelf-life of chicken .