SENSORY AND MICROBIOLOGICAL QUALITY EVALUATION OF VACUUM-PACKED SLICED COOKED CHICKEN BREAST. SHELF-LIFE ESTIMATION

Abstract The shelf-life of vacuum packed, sliced, cooked chicken-breast based on sensory and microbial changes as a function of temperature (2.3, 6.5, 10, 13.5 and 17.7C) was determined. Sensory evaluation and a microbiological study charted the development of lactic acid and psychotropic bacteria and of Brochothrix thermosphacta. Six different sensory methods were used to estimate product shelf-life; of these, the method based on average smell and taste was deemed the most suitable, since these parameters had a greater impact on shelf-life. From a microbiological point of view, mean shelf-life times were estimated at each temperature and compared with the estimates of the tasting panel. In the samples stored at the three lowest study temperatures (2.3, 6.5 and 10C), lactic acid and psychotropic bacteria counts of 10⁷–10⁸ cfu/g were not achieved; this agrees with the absence of sensory rejection at the end of the experiment. At 13.5 and 17.7C, mean shelf-life estimated microbiologically was shorter than that estimated using sensory methods. This difference, which here amounted to at least 8 days, is due to the so-called "delayed change", reported in previous experiments with cooked meat products.     

DYNAMIC MECHANICAL ANALYSIS OF MARINATED CHICKEN BREAST MEAT

Chicken breast muscle was marinated and tumbled in solutions of 7% NaCl and 1.2% of disodium pyrophosphate (DSPP), tetrasodium pyrophosphate (TSPP), tetrapotassium pyrophosphate (TKPP), sodium tripolyphosphate (STPP), or glass phosphate. Dynamic mechanical thermal analysis was used to measure storage modulus and Tan δ as samples were heated from 25 to 75C. For untreated samples, four thermal transitions were noted with the most significant transition at 55.8C. Addition of NaCl and phosphate reduced the number of distinct events, and decreased the major transition to temperatures around 46–48C. Uncooked, marinated samples had lower G' and Tan δ. Treated samples also showed an increase in G' over the 25–45C range. Heating caused the greatest changes in treated samples, with values of G'_75C and Tan δ_75C similar to untreated samples. Different phosphate types resulted in significant differences in G' and Tan δ values. G' values correlated well with Young's modulus, but not with Warner-Bratzler shear values or expressible moisture. Results are discussed in terms of changes in muscle proteins resulting from exposure to NaCl and phosphates, as well as to heat.     

ACIDIFIED SODIUM CHLORITE, TRISODIUM PHOSPHATE AND POPULATIONS OF CAMPYLOBACTER JEJUNI ON CHICKEN BREAST SKIN

The present study was designed to determine the effects of acidified sodium chlorite (ASC) and trisodium phosphate (TSP) antimicrobial treatments. Chicken skin samples inoculated with Campylobacter jejuni ATCC 33291 and C. jejuni pc10 (isolated in our laboratory from chicken carcasses) were separately dipped into sterile tap water (control), 0.1% ASC, 10% TSP, 0.1% ASC followed by 10% TSP and 10% TSP followed by 0.1% ASC for 15 s at 25 ± 1C. Campylobacter jejuni counts and pH values were determined after 0, 1, 3 and 5 days of storage at 4 ± 1C. On day 0, reductions were between 1.1–2.5 log for C. jejuni ATCC 33291 and 1.4–2.4 log for C. jejuni pc10, while the reduction effects of all antimicrobials increased (P < 0.001) during the storage period and the bacterial counts reached undetectable levels (<1.0 × 10² cfu/g) on day 5 of storage at 4 ± 1C. The results of this study suggest that introduction of the antimicrobial treatments ASC, TSP and ASC followed by TSP into poultry processing systems could provide an added measure of safety.     

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 .     

EFFECT OF POSTMORTEM AGING ON CHICKEN BREAST MUSCLE SARCOPLASMIC RETICULUM

FSR (fragmented sarcoplasmic reticulum) isolated from chicken breast muscle (Pectoralis major) at 0 hr, 48 hr and 7 day postmortem was purified using linear density gradient centrifugation. The Ca⁺⁺accumulating ability of the FSR was found to increase with postmortem aging. No loss in ATPase activity was noted nor was any significant change observed in the SDS-gel electrophoresis patterns of the proteins with postmortem aging. The FSR from the aged muscle contained a higher proportion of phospholipids These studies indicate that the Ca⁺⁺ sequestering properties of sarcoplasmic reticulum from chicken breast muscle are not impaired during postmortem aging.     

CONSUMER ACCEPTANCE OF HONEY MARINATED CHICKEN

Chicken bone-in breast quarters marinated through injection with lemon-pepper poultry marinade containing 20 or 30% honey were compared to that marinated without honey and commercial marinated chicken. The objectives were to determine (1) consumer acceptance and willingness to buy and the amount to pay for marinated chicken and (2) the effect of honey on instrumental measurements of color and texture. Chicken was roasted at 177C for 1 h to an internal endpoint temperature of 80C and evaluated for acceptance by 67 untrained consumers. All experimental test products had similar hedonic ratings for appearance, color, flavor, taste, tenderness, juiciness, and overall liking. All samples, both experimental and commercial, were acceptable, and most consumers would be willing to buy chicken marinated with the formulations used in this study for the same price that they were paying for similar products.     

EFFECT OF PROCESSING VARIABLES ON MICROBIAL QUALITY AND SHELF-LIFE OF BLUE CRAB (CALLINECTES SAPIDUS) MEAT

The effects of cooking time, cooking method, season, and storage condition on the microbiological quality, sensory characteristics, and shelf-life of crabmeat were determined under commercial processing conditions. Microbial flora content of the meat was inversely proportional (p 0.05) to the cooking time in both total aerobic and anaerobic plate counts after 6 and 9 days at 2.2C during summer. Boiled cooked crabmeat showed higher microbial count (1–2 log cycle) and shorter shelf-lives than 10 and 12 min retort cooked meat. During summer, the shelf-life of the meat as determined by a sensory evaluation, was: 15.5 days at 0.0C; 12.5 days at 2.2C; and 8.5 days at 5.6C.     

SURVIVAL OF CAMPYLOBACTER JEJUNI IN MARINATED AND NONMARINATED CHICKEN PRODUCTS

Consumption of chicken products has been increasing. Most of these products in Finland are sold as fresh marinated pieces in consumer packages. The impact of marination on the survival of enteric pathogens is not known. We studied the survival of Campylobacter jejuni on marinated chicken drumsticks and sliced breast strips stored at a refrigerator temperature of +4C. The marinade was an emulsion of vegetable oil and water with spices, NaCl (5.9% wt/wt) and its pH was adjusted to 4.5 with lactic and acetic acid. The survival of C. jejuni was similar in marinated and nonmarinated chicken drumsticks and strips. The organisms were detected for at least nine days at the higher inoculum level (10¹– 10² CFU/mL) and for at least five days at the lower inoculum level (10¹– 10² CFU/mL). C. jejuni, inoculated into plain marinade and stored at 4C, was detected after 24 h but not after 48 h. Our results revealed that marination procedure used to reduce and prevent the growth of spoilage organisms does not significantly decrease the survival of Campylobacter jejuni in chicken products.     

THE EFFECT OF ULTRAVIOLET IRRADIATION ON SHELF-LIFE AND RIPENING OF PEACHES AND APPLES

“Loring” and “Elberta” peaches and “Golden Delicious” apples were irradiated with UV (254nm) to doses of 0.84 × 10⁴ to 40 × 10⁴ erg/mm² then stored. “Loring” were stored 10 days and “Elberta” 20 days at 12°C. “Golden Delicious” were stored 30 days at 20–25°C in a dark room. Fruit were examined and differences in percentage rot and in physical-chemical properties determined. Percentage rot decreased with increasing UV dose. Fruit were firmer, pH and soluble solids lower and acidity higher for UV-treated than for nontreated peaches; pH was lower and acidity and ascorbic acid higher in UV treated than in nontreated apples. Percentage weight loss was less for UV-treated apples. The results indicated that UV treatment not only reduced storage rots but also delayed ripening of peaches and apples.     

THE EFFECT OF SODIUM POLYPHOSPHATES AND OF DIVALENT CATIONS ON THE WATER HOLDING CAPACITY OF PRE-AND POST-RIGOR CHICKEN BREAST MUSCLE

The water holding capacity (WHC) of natural actomyosin (NAM), of both contracted and uncontracted glycerinated myofibrils and of pre- and post-rigor chicken meat was investigated in the presence and/or absence of sodium pyrophosphate (PP_i), Kena, CaCl₂ and MgCl₂. In these experiments PP_i caused a small decrease in the WHC of NAM which was further decreased either by Ca or even further by Mg. PP_i with or without Ca or Mg had almost no effect on the WHC of glycerinated myofibrils. Pre-rigor meat showed a slight decrease in WHC of PP_i which was further decreased with Mg or even further by Ca. With post-rigor meat the WHC increase with PP_i was decreased by the addition of Mg or even further decreased by the addition of Ca. The actual WHC of pre-rigor meat was almost twice that of post-rigor meat. Once rigor had occurred no major changes in WHC were observed up to 5 days. Kena caused a slight decrease in the WHC of NAM. Using myofibrils and the meat samples, Kena gave an increase in WHC. The addition of Ca and Mg again tended to decrease this WHC.     

腌鱼品质动力学研究及其货架期的预测

对淡腌鳗鱼在5、15、25℃下,不同时间的挥发性盐基氮(TVBN),活茵总数(TVC)以及可滴定酸度等进行监控,建立腌鱼品质变化的动力学模型从而利用Arrhenius方程预测淡腌鳗鱼的货架寿命.结果表明,TVBN的品质变化遵循0级反应模型,而可滴定酸度和TVC遵循1级反应模型.采用TVC作为品质指标其货架寿命(Qs)的预测模型是:Qs=60exp(0-0.955710/T-278)(5℃～15℃),Qs=21exp(-0.4710/T-288)(15℃～25℃).这个模型与感官评定货架寿命比较结果可靠,相对误差小于9%.