Quality changes of ready-to-eat ginseng chicken porridge during storage at 25°C

Ready-to-eat (RTE) ginseng chicken porridge was heated in a retort with an F-value of 4.0 after being packaged in a gas-tight plastic tray (PP/EVOH/PP) with top film (PET/PA/CPP). Various quality changes were investigated during the storage for 28weeks at 25°C. Over the storage period, microorganisms were not detected above 1.0 log cfu/cm(2) (detection limit). The viscosity increased sharply from 775 to 2025cp for initial 4weeks and increased steadily until 16weeks, with a slight reduction thereafter. During the 28weeks of storage, the ratio of residual oxygen and pH decreased from 10.8% and 6.49 to 5.7% and 6.05, while retrogradation degree increased from 0% to 55.9%. Hunter L(?), b(?), and ΔE values increased until 20weeks and remained for the rest of storage. Based on sensory, microbiological and physicochemical evaluations, the RTE ginseng chicken porridge could be marketable for at least 24weeks at 25°C.     

Quality changes of ready-to-eat ginseng chicken porridge during storage at 25 °C

Ready-to-eat (RTE) ginseng chicken porridge was heated in a retort with an F-value of 4.0 after being packaged in a gas-tight plastic tray (PP/EVOH/PP) with top film (PET/PA/CPP). Various quality changes were investigated during the storage for 28 weeks at 25 °C. Over the storage period, microorganisms were not detected above 1.0 log cfu/cm² (detection limit). The viscosity increased sharply from 775 to 2025 cp for initial 4 weeks and increased steadily until 16 weeks, with a slight reduction thereafter. During the 28 weeks of storage, the ratio of residual oxygen and pH decreased from 10.8% and 6.49 to 5.7% and 6.05, while retrogradation degree increased from 0% to 55.9%. Hunter L^⁎, b^⁎, and ΔE values increased until 20 weeks and remained for the rest of storage. Based on sensory, microbiological and physicochemical evaluations, the RTE ginseng chicken porridge could be marketable for at least 24 weeks at 25 °C.     

Quality and shelf life evaluation of emulsion and restructured buffalo meat nuggets at cold storage (4±1°C)

The study was aimed at comparing the physico-chemical characteristics and texture profile of emulsion and restructured buffalo meat nuggets (BMN) and assessing their shelf life at refrigeration temperature (4±1°C). The stability of restructured batter was significantly lower than that of the emulsion form. Emulsion nuggets (EN) had significantly higher product yield, fat content and calories while restructured nuggets (RN) had significantly higher moisture and protein contents. Texture profile analysis revealed that RN had significantly higher cohesiveness, gumminess, chewiness and shear force values. Differences in TBARS values for emulsion and restructured nuggets were not significant at any particular storage time. Throughout storage, counts for mesophilic, psychrotrophic and coliforms did not exceed log(10)3.09 and 3.44cfu/g, log(10)2.23 and 2.11cfu/g, log(10)1.30 and 1.30cfu/g for emulsion and restructured buffalo meat nuggets, respectively. In spite of a higher overall acceptance for EN initially, panelists rated them considerably lower compared to RN during subsequent storage. Buffalo meat nuggets were acceptable for at least 20 days in cold storage (4±1°C) under aerobic conditions in polypropylene bags.     

Determination of biogenic amines in fresh unpacked and vacuum-packed beef during storage at 4°C

Biogenic amines, putrescine, cadaverine, and histamine were determined in unpacked and vacuum-packed beef; during storage at 4°C for 12 and 35 days, respectively, under the same conditions. Analysis by High Performance Liquid Chromatography in both kind of samples, showed variation of cadaverine and histamine with an increasing tendency to a definite increase of putrescine. In unpacked samples, maximum mean contents for each amine reached 10.4, 5.2 μg/g for putrescine and cadaverine, respectively (12th day) and 2.2 μg/g for histamine (5th day). The total amine content reached 16.5 μg/g (12th day). After 8 days of storage, organoleptic fall-off began and, on the 12th day, all samples were disqualified. In vacuum packs, amine levels increased after 19 days. Maximum levels were determined for putrescine on the 35th day (36.3 μg/g), for cadaverine on the 26th day (28.9 μg/g) and for histamine on the 35th day (19.0 μg/g). Although the vacuum-packed beef was organoleptically acceptable up to 35 days, the total amine levels were greater than 5 μg/g after the 12th day, indicating a leveling off of quality.     

Effects of combining of smoking and marinating on the shelf life of anchovy stored at 4°C

The quality of smoked and marinated anchovy was investigated in terms of sensory, chemical [total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), peroxide value (PV), fatty acids, free fatty acids (FFA), and pH] and microbiological parameters (total aerobic count (TVC), coliform, Escherichia coli, Salmonella, Staphylococcus aureus) during 7 months of storage. The results of sensory analyses showed that the total appearance, odor-taste, and texture scores decreased gradually during storage period. The results of the chemical analyses also correlated well with the sensory analyses apart from TVBN value. TBA significantly increased (p<0.05) from 1.9 to 4.25 MA/kg after the storage of 6 month. Peroxide value (POV) showed significant fluctuations (p<0.05) during the storage period. Initial TVC of 3.8 log CFU/g increased to 6.2 log CFU/g at the end of storage period. According to results obtained from sensory, chemical, and microbiological analyses, shelf life of this product was about 6 month.     

Effect of different binders on the quality of enrobed buffalo meat cutlets and their shelf life at refrigeration storage (4±1°C)

To enhance the binding and quality of enrobed buffalo meat cutlets (EBMC), a meat emulsion at 0%, 15%, 20% and 25% replaced the cooked meat in the formulation. Emulsion containing products had significantly higher moisture contents and texture scores compared to the control. Emulsion at 20% level could be incorporated in enrobed buffalo meat cutlets to enhance their quality. Addition of 1% egg white powder improved the quality of EBMC compared to control, while a 3% level had adverse effect on the sensory attributes despite giving higher product yield and lower shrinkage. Cutlets with refined wheat flour had significantly higher protein and fat contents. It had also higher acceptability followed by corn flour, potato starch and tapioca flour. TBARS of enrobed samples remained lower than controls throughout the storage period. Mesophilic count remained below log3cfu/g for both samples during storage. Uncoated products and enrobed products were acceptable up to 10th and 15th day, respectively. Enrobing of buffalo meat cutlets improved their acceptability and shelf life under refrigeration storage.     

Effect of α-tocopherol on lactone formation in marbled beef and changes in lactone volatility during storage

Dynamic-headspace sampling with a standard-addition method was employed to quantitatively analyze aliphatic lactones in rendered fat from marbled beef and to evaluate the effect of the matrix on volatility. Further, the effects of different levels of the antioxidant α-tocopherol on lactone formation were examined. The slopes of the linear regression curves from the standard-addition method were significantly changed (P < 0.05 or 0.01) for all lactones after storage, with the exception of γ-octalactone, indicating the volatility of the longer-chain lactones were increased after storage. The concentrations of γ-lactones were increased after 7 d of storage at 2 °C (P < 0.01), and the α-tocopherol content in the meat affected the formation of γ-octalactone (P < 0.05) and γ-nonalactone (P < 0.01). The greatest increase was observed for γ-nonalactone in the lowest α-tocopherol (2.9 ppm) group: the concentration of 51.4 ppb was 11.7-fold higher than that before storage. Meanwhile, δ-tetradecalactone in the highest α-tocopherol (28.8 ppm) group showed the highest concentration for the lactones at 415.8 ppb, which was 2.6-fold higher than the concentration before storage. The effect of α-tocopherol was unclear for the δ-lactones. The results indicate that most of the γ-lactones are produced by oxidation during storage but that the other lactones are also generated by other processes as well.     

Quality changes during storage of cooked and sliced meat products measured with PTR-MS and HS-GC–MS

The changes in the VOC composition of industrially produced saveloy were measured with Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS) and HeadSpace Gas chromatography–mass spectrometry (HS-GC–MS) during a six weeks storage period. A decrease in the volatile organic compounds contributing to the fresh aroma of saveloy was the main change observed with both PTR-MS and HS-GC–MS. Samples of four other types of cooked and sliced meat product were measured with PTR-MS in the middle and at the end of the four week shelf-life period. These measurements showed an increase in m/z 69, 71, 87 and 89 for the pork loin and in m/z 61 for the herbal saveloy samples. These ions were assigned to the microbial spoilage markers: acetic acid, 2- and 3-methylbutanol, 2- and 3-methylbutanal, diacetyl and acetoin. Overall, this study shows that PTR-MS has potential for quality control of cooked and sliced meat products.     

Effects of three preservative agents on the shelf life of vacuum packaged Chinese-style sausage stored at 20°C

The influence of 3% sorbitol, 3% sodium lactate and 100 mg/kg nisin on the shelf life of vacuum packaged Chinese-style sausage stored at 20°C was studied. Growth of microbiological populations (aerobe, anaerobe, lactic acid bacteria, leuconostocs) and slime formation on the sausage were not retarded during storage by addition of nisin. Sorbitol lowered the initial water activity of the sausage, however, microbiological spoilage accompanied with pH decline, increase in volatile basic nitrogen compounds and a sour odour defect were observed after 10 days storage. Sodium lactate was bacteriostatic as it inhibited microbial as well as chemical changes during storage so that the shelf life was 25 days at 20°C. The dextran content of the vacuum packaged Chinese-style sausage indicated the spoilage 2-3 days earlier than that seen by other chemical assays or sensory evaluation.     

Quality of giant freshwater prawn (Macrobrachium rosenbergii) during the storage at −18°C as affected by different methods of freezing

This study investigated the effects of liquid nitrogen quick-freezing, ?35°C air-blast freezing, and ?18°C refrigerator direct-freezing on quality retention of frozen giant freshwater prawns using various indicators: microscopic structure, physicochemical, texture, and color properties. The results showed that the shelf lives of prawns treated with liquid nitrogen quick-freezing, ?35°C air-blast freezing, and ?18°C refrigerator direct-freezing were about 20, 12, and 8 weeks, respectively, in terms of total volatile basic nitrogen content and K-value. Meanwhile, liquid nitrogen quick-freezing could effectively improve texture property of frozen giant freshwater prawn. These findings confirm that liquid nitrogen quick-freezing is a promising method to extend the shelf life of frozen prawns.     

Development of shelf stable pork sausages using hurdle technology and their quality at ambient temperature (37±1°C) storage

Shelf stable pork sausages were developed using hurdle technology and their quality was evaluated during ambient temperature (37±1°C) storage. Hurdles incorporated were low pH, low water activity, vacuum packaging and post package reheating. Dipping in potassium sorbate solution prior to vacuum packaging was also studied. Reheating increased the pH of the sausages by 0.17units as against 0.11units in controls. Incorporation of hurdles significantly decreased emulsion stability, cooking yield, moisture and fat percent, yellowness and hardness, while increasing the protein percent and redness. Hurdle treatment reduced quality deterioration during storage as indicated by pH, TBARS and tyrosine values. About 1 log reduction in total plate count was observed with the different hurdles as were reductions in the coliform, anaerobic, lactobacilli and Staphylococcus aureus counts. pH, a(w) and reheating hurdles inhibited yeast and mold growth up to day 3, while additional dipping in 1% potassium sorbate solution inhibited their growth throughout the 9 days storage. Despite low initial sensory appeal, the hurdle treated sausages had an overall acceptability in the range 'very good' to 'good' up to day 6.     

A comparison of the effects of storage of raw milk at 2°C and 6°C on the yield and quality of Cheddar cheese

The advantages of storing raw milk, which is to be used for Cheddar cheese manufacture, at 2°C rather than at 6°C was examined. Storage of milk at the lower temperature effectively reduced the level of psychrotroph growth, and after 4 days the psychrotroph counts in samples stored at 2°C were 100-fold lower than those found in samples stored at 6°C. There was no advantage in terms of cheese yield in storing milks at the lower temperature, but an overall improvement in cheese quality was noted in samples produced from milk stored at 2°C.     

Effect of antibacterial treatments and natural chemicals on the quality and safety of marinated raw crab paste during storage at −20°C

The effects of antibacterial treatments and several natural chemicals on the quality and safety of crab paste during storage at −20°C were investigated. All antibacterial treatments significantly reduced the bacterial total viable count (TVC) of swimming crabs, with sodium hypochlorite (NaClO) combined with ultrasonic cleaning having the best effects. Four chemicals significantly inhibited the increase in TVC, pH, and the accumulation of total volatile basic nitrogen (TVB-N) compared to controls, and their combined treatment had synergistic effects. The L ₉(3 ⁴) orthogonal experiment showed that the optimum combination was A₁B₃C₃D₂ (i.e., 0.1 g kg⁻¹ nisin, 0.4 g kg⁻¹ ε-polylysine hydrochloride, 0.3 g kg⁻¹ tea polyphenol, and 0.5 g kg⁻¹ citric acid). The TVC, TVB-N concentration, and pH in A₁B₃C₃D₃-treated samples remained far below the maximum acceptable limit for good-quality marinated, raw, aquatic animal product after 12 months of frozen storage at −20°C. Furthermore, the combined treatment (A₁B₃C₃D₃) significantly inhibited the reproduction of foodborne pathogenic bacteria and spoilage bacteria. The antibacterial treatments and natural chemicals reduced foodborne pathogenic bacteria and inhibited microbial spoilage, and therefore maintained the quality and safety of crab paste during frozen storage. Antibacterial treatments and natural chemicals could be commercially utilized to maintain the quality and safety of crab paste.     

Effect of Eryngium caeruleum essential oil on microbial and sensory quality of minced fish and fate of Listeria monocytogenes during the storage at 4°C

The present study investigated in vitro antimicrobial activity of Eryngium caeruleum essential oil (EEO) against five foodborne pathogenic bacteria based on microdilution and disk diffusion methods. Moreover, its effects on specific spoilage microorganisms, inoculated Listeria monocytogenes, and its sensory changes in minced fish were evaluated during 12 days of storage at refrigeration temperature. The results showed that Staphylococcus aureus and Escherichia coli were the most sensitive and the most resistant bacteria with a minimum inhibitory concentration of 0.125 and 1 mg/ml, as well as inhibition zones of 15.66 and 11.66 mm, respectively. Regarding the antimicrobial effect of EEO on the microbial profile and inoculated L. monocytogenes, treating with 0.4% EEO caused a significant decrease in the studied microorganisms when compared to the control group (p < 0.05). In addition, considering the sensory evaluation, the best scores were observed for the samples treated with 0.2% and 0.4% EEO. However, none of the groups obtained acceptable scores until the final day of storage except for the color attribute. In general, sensory evaluation and its correlation with microbial counting indicated that the treatment with 0.4% EEO was able to preserve the microbial quality of the minced fish at refrigeration temperature without any undesirable sensory effects.     

Effects of ozonation on microbiological,chemical and sensory attributes of vacuum-packaged rainbow trout stored at 4±0.5°C

The effects of ozone in aqueous solution on the shelf life of whole, vacuum-packaged rainbow trout, stored under refrigeration (4±0.5°C) were studied by monitoring the microbiological, chemical and sensory changes for a period of 15 days. Vacuum-packaged non-ozonated trout served as the control sample. Ozonation affected populations of bacteria namely, mesophilic aerobic bacteria, Pseudomonas spp. and H₂S-producing bacteria until day 11 of storage, Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae until day 8 of storage. Trimethylamine (TMA) values of all rainbow trout samples remained low (<3 mg N/100 g) until day 11 of storage, and then increased to 12.2, 8.9 and 4.7 mg N/100 g for the control and the samples ozonated for 60 and 90 min, respectively on day 15 of storage. Total volatile basic nitrogen (TVB-N) values remained relatively constant (20–25 mg N/100 g) until day 11 of storage, but increased to 61.1, 37.6 and 39.4 mg N/100 g flesh for the control and ozonated specimen for 60 and 90 min, respectively on day 15 of storage. Thiobarbituric acid (TBA) values remained relatively constant (1–3 mg MA/kg flesh) until day 12 of storage but increased to 8.4, 6.4 and 3.8 mg MA/kg flesh on day 15 of storage for the control and the ozonated trout for 60 and 90 min, respectively. Sensory evaluation (odor, taste and texture) of cooked rainbow trout showed a very good correlation with bacterial populations. On the basis of both sensory and microbiological data, a shelf life of 10 and 12 days was obtained for ozonated, vacuum-packaged and refrigerated rainbow trout at 60 and 90 min, respectively.     

Survival of Listeria monocytogenes introduced as a post-aging contaminant during storage of low-salt Cheddar cheese at 4, 10, and 21°C

Traditional aged Cheddar cheese does not support Listeria monocytogenes growth and, in fact, gradual inactivation of the organism occurs during storage due to intrinsic characteristics of Cheddar cheese, such as presence of starter cultures, salt content, and acidity. However, consuming high-salt (sodium) levels is a health concern and the dairy industry is responding by creating reduced-salt cheeses. The microbiological stability of low-salt cheese has not been well documented. This study examined the survival of L. monocytogenes in low-salt compared with regular-salt Cheddar cheese at 2 pH levels stored at 4, 10, and 21°C. Cheddar cheeses were formulated at 0.7% and 1.8% NaCl (wt/wt) with both low and high pH and aged for 10 wk, resulting in 4 treatments: 0.7% NaCl and pH 5.1 (low salt and low pH); 0.7% NaCl and pH 5.5 (low salt and high pH); 1.8% NaCl and pH 5.8 (standard salt and high pH); and 1.8% NaCl and pH 5.3 (standard salt and low pH). Each treatment was comminuted and inoculated with a 5-strain cocktail of L. monocytogenes at a target level of 3.5 log cfu/g, then divided and incubated at 4, 10, and 21°C. Survival or growth of L. monocytogenes was monitored for up to 90, 90, and 30 d, respectively. Listeria monocytogenes decreased by 0.14 to 1.48 log cfu/g in all treatments. At the end of incubation at a given temperature, no significant difference existed in L. monocytogenes survival between the low and standard salt treatments at either low or high pH. Listeria monocytogenes counts decreased gradually regardless of a continuous increase in pH (end pH of 5.3 to 6.9) of low-salt treatments at all study temperatures. This study demonstrated that post-aging inoculation of L. monocytogenes into low-salt (0.7%, wt/wt) Cheddar cheeses at an initial pH of 5.1 to 5.5 does not support growth at 4, 10, and 21°C up to 90, 90, and 30 d, respectively. As none of the treatments demonstrated more than a 1.5 log reduction in L. monocytogenes counts, the need for good sanitation practices to prevent post-manufacturing cross contamination remains.     

Survival of Salmonella serovars introduced as a post-aging contaminant during storage of low-salt Cheddar cheese at 4, 10, and 21 °C

The microbiological stability of low-salt cheese has not been well documented. This study examined the survival of Salmonella in low-salt compared to regular salt Cheddar cheese with 2 pH levels. Cheddar cheeses were formulated at 0.7% and 1.8% NaCl (wt/wt) with both low and high-pH and aged for 12 wk resulting in four treatments: 0.7% NaCl and pH 5.1 (low-salt and low-pH); 0.7% NaCl and pH 5.5 (low-salt and high-pH); 1.8% NaCl and pH 5.7 (standard-salt and high-pH); and 1.8% NaCl and pH 5.3 (standard-salt and low-pH). Each treatment was comminuted and inoculated with a 5-serovar cocktail of Salmonella at a target level of 4 log CFU/g, then divided and incubated at 4, 10 and 21 °C for up to 90, 90, and 30 d, respectively. Salmonella counts decreased by 2.8 to 3.9 log CFU/g in all treatments. In the initial period of survival study, standard-salt treatments exhibited significantly lower Salmonella counts compared to low-salt treatments. The pH levels did not exhibit obvious significant effect in the Salmonella survival in low-salt treatments. Salmonella counts declined gradually regardless of a continuous increase in pH (end pH of 5.3 to 5.9) of low-salt treatments at all study temperatures. Salmonella counts were reduced faster at 21 °C storage. Although there were significant reductions in Salmonella counts, the treatments demonstrated survival of Salmonella for up to 90 d when stored at 4 or 10 °C and for up to 30 d at 21 °C, the need for good sanitation practices to prevent postmanufacturing cross contamination remains. PRACTICAL APPLICATION: Low-salt aged Cheddar cheese could not support the growth of inoculated Salmonella and in fact gradual reduction in Salmonella count occurred during storage. Besides being nutritionally better, low or reduced salt Cheddar are safe as their full salt counterparts and that salt may only be a minor food safety hurdle regarding the post-aging contamination and growth of Salmonella. However, the treatments could not demonstrate complete destruction of Salmonella for up to 90 d when stored at 4 or 10 °C and for up to 30 d at 21 °C, the need for good sanitation practices to prevent postmanufacturing cross-contamination remains.     

Proteome changes of fresh-cut Zizania latifolia during refrigerated (1?°C) storage

The total proteins from the fresh-cut Zizania latifolia during refrigerated storage were extracted and separated by two-dimensional electrophoresis (2-DE). A total of 657 protein spots were detected on the gels, among which 33 spots showed a significant change in protein abundance based on twofold difference. Using MALDI-TOF/TOF, 25 spots were identified, which were classified into five functional categories that included cell structure (32?%), stress response and defense (28?%), ripening and senescence (8?%), signal transduction (8?%), and unclear functional proteins (24?%). Of the 25 differentially expressed proteins, 10 were up-regulated and 15 were down-regulated. Among 10 up-regulated spots, 5 were related to cell structure, 2 to oxidative stress, 1 to ripening and senescence, 1 to signal transduction, and 1 to unclear functional proteins. For the 15 down-regulated spots, 5 were related to stress response, 3 to cell structure, 1 to ripening and senescence, 1 to signal transduction, and 5 to unclear functional proteins. These results indicate that specific proteins expressed in fresh-cut Z. latifolia during storage at 1?°C show a coordinated response to cope with wounding stress caused by fresh-cut processing.