Effects of Different Whey Protein Concentrate Coating on Selected Properties of Rainbow Trout (Oncorhynchus mykiss) During Cold Storage (4°C)

In this study, the effect of different whey protein concentrate coating formulations (with or without glycerol) on the storage of fillets over a period of 15 days at 4ºC was investigated. Fillets were conducted to microbiological, chemical, and sensory analyses. Difference in microbiological and chemical changes between samples was found to be significant (p < 0.05) during storage period. The Y and Z were preferred more by the panellists, while C samples received the lowest scores. According to the results of microbiological analyses, shelf life of fillets was estimated at 6, 9, 12, and 15 days for C, X, Y, and Z samples, respectively.     

Effects of Vacuum Packaging and Wrapping with Chitosan-Based Edible Film on the Extension of the Shelf Life of Sea Bass (Dicentrarchus labrax) Fillets in Cold Storage (4 °C)

In the present study, we assessed the possibility of improving the shelf life of fresh sea bass (Dicentrarchus labrax) fillets by using vacuum packaging and wrapping with chitosan-based edible films during cold storage at 4 °C. Sea bass fillet samples were periodically evaluated to assess chemical (pH, trimethylamine and total volatile basic nitrogen) and microbiological (presence of mesophilic aerobic bacteria and psychrotrophic bacteria) quality. Chemical spoilage (trimethylamine and total volatile basic nitrogen) and growth of microorganisms (total mesophilic and total psychrophilic aerobic bacterial counts) were significantly reduced (P?≤?0.05) in vacuum-packaged chitosan film wrapping during cold storage at 4 °C. The results showed that the shelf life of the control and vacuum-packaged groups ended within 5 days, whereas that of vacuum-packaged chitosan film-wrapped samples ended at 25 to 30 days. Therefore, the shelf life of sea bass fillets wrapped in chitosan was prolonged by about 20 days.     

Changes in quality of rainbow trout (Oncorhynchus mykiss) fillets preserved with salt and sugar at low concentrations and stored at 4°C

The effects of dry-curing with low concentrations of salt and sugar on the quality of rainbow trout (Oncorhynchus mykiss) fillets were studied over a 16-day storage period at 4°C. Physicochemical characteristics (total volatile base nitrogen (TVB-N), biogenic amines (BAs), ATP-related compounds and K value), microbial populations (total aerobic counts (TAC), H₂S-producing bacteria, Pseudomonas, Aeromonas, and lactic acid bacteria) and sensory (SA) indicators were analyzed. Fish samples were subjected to the following treatments: untreated (control), dry-cured with 1.3% salt (T1), and dry-cured with 1.3% salt that also contained 0.9% sugar (T2). SA indicated that the sensory quality of the control, T1, and T2 was unacceptable after 8, 12, and 12 days of storage, respectively. Moreover, the cadaverine concentration of treated samples was significantly lower (P < 0.05) than the control after storing for 8 days. T1 and T2 were significantly higher (P < 0.05) than the control in inosine 5-monophosphate (IMP) content from the 2th to 10th day. Cadaverine, putrescine, hypoxanthine, and TAC were correlated significantly (P < 0.01) with SA, and these seemed to be reliable indicators of fish quality. The results indicated that curing treatments extended the shelf life of rainbow trout fillets, which could be exploited by processors.     

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.     

Survival and growth of foodborne pathogens in minimally processed vegetables at 4 and 15 °C

Abstract: We conducted this study to investigate the survival and growth of pathogens on fresh vegetables stored at 4 and 15 °C. Vegetables (romaine lettuce, iceberg lettuce, perilla leaves, and sprouts) were inoculated with 4 pathogens (Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli O157:H7) and stored at 2 different temperatures for different periods of time (3, 6, 9, 12, and 15 d at 4 °C and 1, 2, 3, 5, and 7 d at 15 °C). Populations of the 4 pathogens tended to increase on all vegetables stored at 15 °C for 7 d. Populations of E. coli O157:H7 and S. Typhimurium increased significantly, by approximately 2 log₁₀CFU/g, on loose and head lettuce stored at 15 °C for 1 d. No significant differences were observed in the growth of different pathogens on vegetables stored at 4 °C for 15 d. E. coli O157:H7 did not survive on sprouts stored at 15 or 4 °C. The survival and growth of food pathogens on fresh vegetables were very different depending on the pathogen type and storage temperature. Practical Application: Survivals and growth of pathogens on various vegetables at 4 and 15 °C were observed in this study. Survivals and growth of pathogens on vegetables were different depending on the pathogen type and storage temperature. Therefore, vegetables should be stored under refrigerated conditions (below 4 °C) prior to consumption. This recommendation may vary depending on the type of vegetable.     

Effects of curdlan on the texture and structure of Alaska pollock surimi gels treated at 120°C

The effects of curdlan (2%, 3% and 4%) on the gel properties of Alaska surimi using high-temperature treatment were examined in this study. Curdlan treatment improved the gel strength of surimi in a concentration-dependent manner. Based on the results of dynamic rheology and differential scanning calorimetry (DSC), curdlan promoted the stability of proteins in the gel. Moreover, curdlan facilitated the interaction between gel proteins and actomyosin, thereby preventing the aggregation and denaturation of protein and increased the thermal transition temperature. The results of scanning electron microscopy showed that the addition of curdlan induced the formation of a more ordered and denser gel matrix and the fibrils in the three-dimensional network became more delicate. Therefore, surimi samples with curdlan may hold more moisture and exhibit improved transfer of free water to bound water, leading to a higher water-holding capacity (WHC).     

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.     

Detection of specific spoilage bacteria from fish stored at low (0°C) and high (20°C) temperatures

The spoilage potential of 309 bacterial strains isolated from fish spoiled at 0 and 20°C was investigated. Gram-negative, non-fermentative, motile rods tentatively identified as Alteromonas were the major spoilage organisms at 0°C. These bacteria were also found at 20°C, but a large number of Gram-negative, fermentative, motile rods belonging to the Vibrionaceae were also identifieas spoilage organisms at this temperature. Most of the Vibrionaceae did, however, not produce hydrogen sulphide from thio-sulphate but only from the sulphur containing amino acid, L-cysteine. A specific count of fish spoilage organisms at both low and high temperatures could therefore be obtained directly on an Iron Agar containing thiosulphate and cysteine where bacteria capable of forming H₂S from either source of sulphur would appear as black colonies.     

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.     

Effects of aluminium foil and cling film on biogenic amines and nucleotide degradation products in gutted sea bream stored at 2±1 °C

Biogenic amines and nucleotide degradation products of sea bream stored in ice, wrapped in aluminium foil (WAF) and in cling film (WCF) at 2±1 °C were investigated by using a rapid HPLC method. Results obtained from this study showed that for household purposes packing fish in different materials has a little effect on the biogenic amines formation and nucleotide degradation products. The highest decrease of IMP content was observed for sea bream in WAF, followed by WCF. INO values showed a fluctuation and remained below the levels of 5.5 μmol/g for all storage conditions. Hx value constantly increased with the storage time during chilled storage. For all of the storage condition, K and Ki value increased linearly with storage time. At the end of the storage period, K, Ki, H and G value reached 60–76%, 65–81%, 30–54% and 89–173%, respectively. Among biogenic amines, (trimetylamine) TMA, putrescine, cadaverine, spermidine, spermine, tryptamine, tyramine, β-phenylalanine and histamine were detected during storage period. TMA and putrescine were observed to increase linearly during storage period. Histamine production was only found at the end of storage period. The highest histamine values for fish wrapped in aluminium foil were 6.4 mg/100 g and fish wrapped in cling film was 4.6 mg/100 g.     

The effects of nanoemulsions based on citrus essential oils (orange,mandarin, grapefruit,and lemon) on the shelf life of rainbow trout (Oncorhynchus mykiss) fillets at 4 ± 2°C

This study investigated the antioxidant and antimicrobial effects of nanoemulsions of orange, grapefruit, mandarin, and lemon essential oils on rainbow trout fillets stored at 4 ± 2°C in refrigerator. The results demonstrated that the shelf life of the rainbow trout fillets was determined as 10 days for the control group, 12 days for the tween 80 (surfactant), 14 days for orange and lemon treatment groups, and 16 days for mandarin and grapefruit groups. Nanoemulsions based on essential oils removed the fishy odor and had a positive effect on organoleptic quality. The use of citrus essential oil-based nanoemulsions decreased the values of biochemical parameters and slowed the growth of bacteria compared to the control group. Among all treatment groups, only the control group exceeded the TVB-N limit value on the 12th day of storage. PV and FFA values in fillets treated with mandarin and grapefruit nanoemulsions developed more slowly during the storage period. In addition, the lowest bacteria counts were found in the mandarin and grapefruit treatment groups. It can be concluded that especially mandarin and grapefruit EOs in all citrus essential oils can be recommended for preparing nanoemulsions in the preservation of rainbow trout fillets.     

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.     

Quality Changes of Whole and Fresh-Cut Zizania latifolia During Refrigerated (1 °C) Storage

The quality changes of whole and fresh-cut Zizania latifolia were investigated for 12 days at 1 °C. The results showed that the respiratory rate of whole Z. latifolia increased over the first 9 days of storage and then decreased quickly. Weight loss and cellulose and lignin contents increased, while whiteness index (WI), firmness, and total sugar content diminished. Polyphenol oxidase (PPO) and peroxidase (POD) activities decreased for the first 3 days and then increased, whereas the activities of SOD, APX, and CAT increased and reached a peak value on the 3rd, 6th, and 9th days, respectively. Fresh-cut exhibited higher respiratory rate, weight loss, and cellulose and lignin contents and lower WI, firmness, and total sugar content; activities of PPO, POD, superoxide dismutase, ascorbate peroxidase, and catalase were enhanced compared with whole Z. latifolia. However, most of these quality attributes were similar for cut and whole Z. latifolia samples during the first 6 days of storage, suggesting that storage at 1 °C delayed quality deterioration thereby extending the shelf life of packaged fresh-cut Z. latifolia.     

Effects of different ATP contents on phosphorylation level of glycogen phosphorylase and its activity in lamb during incubation at 4 ℃ in vitro

The aim of this study was to investigate the effects of ATP on glycogen phosphorylase activity in lamb during incubation at 4℃ in vitro. Sarcoplasmic proteins from lamb were extracted and treated with different contents of ATP to get three groups of glycogen phosphorylase with low, middle and high ATP content groups, the amount of ATP were 0.5, 2.0 and 2.5 μM per 100 μg protein, respectively. The control group was without ATP adding. The results showed that ATP promoted the phosphorylation of glycogen phosphorylase, and phosphorylation modification promoted its activity. But ATP inhibited the activity of glycogen phosphorylase and ATP preferentially participated in phosphorylation. When ATP concentration was 0.5 μM per 100 μg protein, the effect of phosphorylation modification on the activity of glycogen phosphorylase was equal to the inhibition of ATP. The effect of glycogen phosphorylase phosphorylation on its activity gradually became dominant as incubation time prolonged.     

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.     

Quality changes and shelf life of imported vacuum-packaged beef chuck during storage at 0°C

The objective of this study was to investigate differences in adipose tissue fatty acid composition among stress genotypes as well as to determine relationships of those fatty acids with performance, carcass and meat quality traits. Haplotypic analysis of parents and offspring was employed to assign 48 pigs to three stress genotypes of swine. Individual fatty acid profiles were determined on subcutaneous backfat. Stress genotype had a significant effect on the proportions of C14:0 (P<0.05), C16:0 (P<0.10), C16:1 (P<0.05) and C18:0 (P<0.05) fatty acids. After adjusting for stress and gender, there was a negative correlation between backfat thickness and essential fatty acids (linoleic and linolenic) (P<0.001). In contrast, the correlation of loin muscle area with C18:2 (P<0.01) and C18:3 (P<0.001) was positive. The degree of fat firmness was negatively correlated to the proportion of total unsaturated fatty acids (P<0.01). No significant correlations were observed between fatty acid contents and lean meat quality traits.