Fishmeal-based diet decreases the redness of sunshine bass (Morone chrysops × Morone saxatilis) fillets

The objectives of the present study were to determine the effects of feeding a fishmeal-based diet on color attributes and lipid oxidation in sunshine bass (Morone chrysops × Morone saxatilis) fillets during retail display. A balanced diet containing 30 percent fishmeal (FM) or a diet containing poultry byproduct meal as a complete replacement of fishmeal (PB) was fed to sunshine bass for fifteen months. Harvested fish were filleted, overwrapped with polyvinyl chloride film and stored at 2 °C (REF) or over ice (ICE), under an illuminated retail display. Samples (n = 6) were analyzed after 0, 3, 6, or 9 d storage for color attributes (CIE L^∗, a^∗, b^∗, hue angle and chroma), thiobarbituric acid-reactive substances (TBARS), and pH. TBARS and pH increased (P < 0.05) during storage, indicating progress in lipid oxidation and protein changes. FM fillets demonstrated lower (P < 0.05) a^∗ (redness) value and greater (P < 0.05) hue angle than PB fillets. Since consumer acceptance of sunshine bass is dependant upon its white flesh, fishmeal supplementation could be used as a dietary strategy to improve fish marketability.     

Colour changes of fillets of rainbow trout (Oncorhynchus mykiss W.) fed astaxanthin or canthaxanthin during storage under controlled or modified atmosphere

Rainbow trout were fed diets containing two levels of lipids (9 g/100 g and 24 g/100 g) associated with two keto-carotenoid pigments (80 mg of astaxanthin or of canthaxanthin/kg of diet) for 4 months. After slaughter colour stability of fillets was studied during a 4-week storage at +4 °C under controlled (CA) and modified (MA) atmospheres under 100% air, 60:40 N₂-CO₂ mix and 60:40 air-CO₂ mix. Fillets from fish fed high fat level diets showed higher chroma and higher a^* and b^* colour parameters than those from fish fed low fat level diets. Storage time increased lightness and hue angle in CA but only lightness under MA. After storage at +4 °C lightness of fish fillets stored under MA were lower (P<0.05) than those stored under CA. Carotenoid source resulted in differences in chroma and hue angle of fish fillet stored under CA and MA. Dietary lipid levels resulted in differences in chroma under CA. Under CA the lower (P<0.05) differences between stored-initial values was for N₂-CO₂ and the higher (P<0.05) for air. Under MA, air-CO₂ and N₂-CO₂ gave similar results for L^*, C^* and H(°)_ab. Our experiment demonstrated that colour parameters of fish fillets reacted differently according to gas mixture and storage time.     

Physicochemical changes in ω − 3-enhanced farmed rainbow trout (Oncorhynchus mykiss) muscle during refrigerated storage

Physicochemical changes of ω − 3-enhanced farmed rainbow trout (Oncorhynchus mykiss) fillets developed by dietary modification with flaxseed oil and α-tocopheryl acetate (α-TA) were determined during storage at 2 °C. Trout were fed experimental diets for 120 days followed by processing to obtain boneless skinless fillets. The dietary modification increased concentration of total ω − 3 fatty acids in the fillets, which enhanced chances for lipid oxidation during storage. The fillets were vacuum or non-vacuum packed and stored at 2 °C for 10 or 12 days. Dietary α-TA resulted in higher (P < 0.05) concentration of α-tocopherol in fillets during storage; however, it did not retard (P > 0.05) lipid oxidation. Vacuum packaging resulted in much lower (P < 0.05) TBARS and higher (P < 0.05) retention of α-tocopherol during storage than non-vacuum packaging. However, α-tocopherol unlike vacuum packaging better protected ω − 3 FA in the fillets during storage.     

Effects of brine concentration on shelf-life of hot-smoked tilapia (Oreochromis niloticus) stored at 4 °C

This work evaluated the effect of brine concentration on the shelf-life of hot-smoked tilapia (Oreochromis niloticus) stored at 4 °C. The fish were brined in solutions of 5%, 10%, and 15% NaCl and unsalted fish were used as controls. The fish were then smoked, cooled and stored at 4 °C. Oxidative rancidity measured by the peroxide value (PV), and thiobarbituric acid number (TBA) showed increases with the storage time and also as a result of the increasing salt content in fish muscle. Hot smoked tilapia can be stored safely under refrigerated conditions for over 35 days, and 5% brine was found to be optimal for storage.     

Use of viscera extract from hybrid catfish (Clarias macrocephalus × Clarias gariepinus) for the production of protein hydrolysate from toothed ponyfish (Gazza minuta) muscle

Proteolytic activity of viscera extract from hybrid catfish (Clarias macrocephalus × Clarias gariepinus) was studied. The optimal pH and temperature were 9.0 and 50 °C, respectively, when toothed ponyfish (Gazza minuta) muscle was used as a substrate. When viscera extract from hybrid catfish was used for the production of protein hydrolysate from toothed ponyfish muscle, extract concentration, reaction time, and fish muscle/buffer ratio affected the hydrolysis and nitrogen recovery (NR) (p < 0.05). Optimum conditions for toothed ponyfish muscle hydrolysis were 3.5% hybrid catfish viscera extract, 15 min reaction time and fish muscle/buffer ratio of 1:3 (w/v). High correlation between the degree of hydrolysis (DH) and NR (R² = 0.974) was observed. Freeze-dried hydrolysate had a high protein content (89.02%, dry weight basis) and it was brownish yellow in colour (L^∗ = 63.67, a^∗ = 6.33, b^∗ = 22.41). The protein hydrolysate contained a high amount of essential amino acids (48.22%) and had arginine and lysine as the dominant amino acids.     

Oxidation in HiOx-packaged pork Longissimus muscle predisposes myofibrillar and sarcoplasmic proteins to N-nitrosamine formation in nitrite-curing solution

The effect of meat protein in situ oxidation on the formation of N-nitrosodiethylamine (NDEA) was investigated. Fresh minced pork was untreated (Con) or treated with 700 mg/kg α-tocopherol (Toc) or 300 mg/kg tea polyphenols (PPE), packaged in a HiOx atmosphere (78.8% O₂, 18.8% CO₂, 2.4% N₂), then stored at 2 ± 1 °C for up to 10 days. Crude myofibrillar (MP) or sarcoplasmic (SP) protein (20 mg/mL) extracted from stored meat was reacted with 43 μM sodium nitrite at 80 °C for 1 h. Lipid oxidation was totally inhibited in PPE pork but increased in Con and Toc samples after 10 days. There was significant protein oxidation (losses of sulfhydryls, formation of protein carbonyls) in both MP and SP in all samples during storage. However, the Con group suffered more extensive protein oxidation than Toc and PPE and produced more NDEA (P < 0.05), indicating that protein oxidation promoted nitrosation.     

Evaluation of the performance of osmotic dehydration sheets on freshness parameters in cold-stored beef biceps femoris muscle

This study aimed to evaluate the effects of osmotic dehydration sheet (ODS) packaging on the quality parameters of beef biceps femoris muscle samples stored at 4 °C for 0, 1, 3 and 7 days. Quality indices such as Hunter color values (L^∗, a^∗ and b^∗, the percentage of metmyoglobin (Met-Mb%), K value (freshness index), and the contents of adenosine triphosphate (ATP)-related compounds (ARCs), thiobarbituric acid reactive substances (TBA-RS) and volatile basic nitrogen (VBN) were measured. ODS gave lower a^∗ and b^∗ values and lower Met-Mb% compared with control samples wrapped in polyvinylidene chloride film (PVDCF) (P < 0.01), but had no effect on L^∗ (P < 0.01). As a result, with higher levels of osmotic dehydration produced by the ODS, the percentage of weight loss and the total contents of ARCs and inosine monophosphate of the samples also increased (P < 0.05). The K values of ODS samples were also significantly lower than PVDCF-wrapped samples (P < 0.05). Low performance ODS wrapping reduced the TBA-RS values below those found with PVDCF and high performance ODS processing (P < 0.01). Moreover, the use of ODS had no effect on VBN values. Thus, although the bright red of beef samples changed to a dark purple color and the weights of samples decreased, the ODS approach has potential as a tool for decreasing the deterioration of other quality indices such as Met-Mb%, TBA-RS, ARCs, K values and the VBN content of cold-stored beef.     

Stability of potassium iodide and omega-3 fatty acids in fortified freshwater fish emulsion sausage

Oxidative stability of emulsion sausages prepared from African walking catfish (AF: Clarias gariepinus) and rohu (RH: Labeo rohita) fortified with three levels of the refined tuna oil (2%, 6%, and 10%) with 150 μg KI/100 g sample and without KI was investigated. The control was prepared using 20% soybean oil and without KI. Samples were vacuum-packed and stored at 4 °C. Iodine content decreased approximately 14% after cooking and remained constant throughout storage. Sausages fortified with tuna oil showed higher level of n-3 (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)), but lower level of n-6 fatty acids (P<0.05) than the control. The ratio of n-6 to n-3 fatty acids of all samples decreased with an increase of tuna oil addition and was stable throughout 4 weeks of storage. Degradation of linoleic (LA) and linolenic acid (LNA) mainly occurred in the samples added 2% tuna oil whereas samples fortified with higher tuna oil (6-10%) exhibited higher loss of EPA and DHA. Hydroperoxide (HPV) and thiobarbituric reactive substances (TBARS) values were increased as addition level of tuna oil increased. Textural properties were not affected during storage at 4 °C for up to 4 weeks (P<0.05). Based on lipid stability results, 2% fortification of the refined tuna oil was recommended for emulsion sausage prepared from both species. Addition of 150 μg KI/100 g had no effect on lipid oxidation of fish sausages (P<0.05).     

Cold storage conditions affect the persistence of diphenylamine, folpet and imazalil residues in ‘Pink Lady’ apples

‘Pink Lady^®’ apples (Malus domestica) fruit were harvested at commercial maturity treated with three different agrochemical products, and stored at 1 °C under either air or controlled atmosphere conditions (2.5 kPa O₂ + 3 kPa CO₂ and 1 kPa O₂ + 2 kPa CO₂) for 15 and 28 weeks. Diphenylamine, folpet and imazalil contents in both skin and flesh were simultaneously determined after cold storage plus a simulated marketing period of 1 or 7 days at 20 °C. Results showed that apples stored in 2.5 kPa O₂ + 3 kPa CO₂ retained higher contents of diphenylamine residues in comparison with those stored in 1 kPa O₂ + 2 kPa CO₂ or refrigerated air. Significant differences in imazalil skin contents were found throughout the simulated marketing period at 20 °C after storage for 28 weeks in controlled atmospheres.     

Cooking quality of faba bean after storage at high temperature and the role of lignins and other phenolics in bean hardening

Selected physical and chemical characteristics of faba beans (Vicia faba L.) cv. Fiesta were studied after 12 months storage at 5, 15, 25, 37, 45 or 50 °C (±2 °C) in relation to the hard-to-cook phenomenon. In comparison with control (seeds stored at 5 °C), seeds stored at 15 and 25 °C demonstrated non-significant (p?0.05) changes in most of the physical and chemical characteristics including hydration and swelling coefficients, acid detergent fibre, lignin and tannin contents, whereas seeds stored at ?37 °C demonstrated significant changes (p?0.05). Solutes and electrolytes leaching after 18 h soaking substantially increased with increased temperature. Faba bean hardness tested by the hard-to-cook test also increased substantially with increased storage temperature. After 8 h soaking followed by 2 h cooking, the puncture force required for seeds stored at 5 °C was 3.3 N seed⁻¹ whereas seeds stored at 50 °C required a much higher puncture force of 15.2 N seed⁻¹. There was a high negative correlation (r²=0.98) between storage temperature and cooking ability of faba bean. Substantial increases in acid detergent fibre and lignin contents occurred with increased storage temperatures. There was a three-fold increase in lignin content of faba bean stored at 50 °C compared to those stored at 5 °C and it was correlated with bean hardness (r²=0.98). Storage at high temperatures for 12 months led to a substantial reduction in total free phenolics especially in the testa and there was a greater reduction with increasing storage temperature. Reduction in free phenolics was negatively correlated (r²=0.75) with bean hardness.     

Quality assessment of wild European eel (Anguilla anguilla) stored in ice

The quality assessment of wild European eel (Anguilla anguilla) stored in ice and in boxes without ice (3 ± 1 °C) was investigated by the sensory analysis, levels of nucleotide breakdown products and biogenic amines for up to 19 days. Sensory analysis was assessed using the Tasmanian Food Research Unit Scheme. K and related values (K_i, G, P, H and F_r) were used as freshness indicators. Linear regressions (r²) obtained from K, K_i, G, P, H and F_r were 0.95, 0.96, 0.83, 0.96, 0.99 and 0.96, respectively, for eel stored in ice whereas, for eel kept in boxes without ice, the values were 0.86, 0.86, 0.96, 0.91, 0.98 and 0.86, respectively. When eel stored in ice and in boxes without ice were considered at the limit of acceptability by assessors at ∼12–14 days and ∼5–7 days, respectively, the average K, K_i and P values were ∼70–85%, H values were ∼60% and F_r values were ∼10% for both storage conditions. The level of histamine exceeded the legal limit (5 mg/100 g fish) in eel stored without ice after 6–7 days and, in ice, after 13–14 days of storage, at which time eels were rejected by the sensory panel. The concentrations of biogenic amines were higher in eel stored in boxes without ice than in eel kept in ice. The levels of histamine in the muscle of eel kept in boxes without ice and in ice increased to the maximum levels of 17.9 mg/100 g on day 12 and 12.6 mg/100 g on day 19, respectively.     

Freshness assessment of ray fish stored in ice by biochemical,chemical and physical methods

Ray fish were caught, filleted, and stored in ice. Fillets were analysed for 18 days to determine the chemical, biochemical and physical changes and their relation to the muscle eating quality. Trimethylamine (TMA-N), total volatile bases (TVB-N), ATP content and breakdown products, K value, pH, texture, water-holding capacity (WHC) and colour changes were monitored. At the beginning of the study, the ray fish muscle showed a low concentration of ATP and a high value of inosine 5′-monophosphate (IMP). Regarding to the signs of freshness and deterioration, K value presented an exponential increase (r2 = 0.95) with an initial value of 4.7% and a final value of 47.5%. Furthermore, the TBV-N and TMA-N significantly increased (P < 0.05) during the storage in ice. As for the physical analysis whereas the texture changed (P < 0.05); pH and the WHC were not affected (P < 0.05). The overall results of this study indicated that the edible quality of ray fish muscle was maintained during at least 15 days of ice storage.     

Effects of cold storage, rearing temperature, parasitoid age and irradiation on the performance of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae)

In this study, the effects of cold storage, rearing temperature, parasitoid age, and irradiation on the performance of the egg parasitoid Trichogramma evanescens were investigated. Pupae of T. evanescens can be stored at 4 °C for up to 3 weeks without much loss of performance. The longevity and walking speed of adults emerging from chilled pupae significantly decreased after longer storage periods. The F₁ generation of adults which emerged from pupae stored up to 3 weeks was able to parasitize as well as the control. The parasitization rate was similar at 24, 27, and 30 °C, but significantly decreased at 33 and 36 °C. Although T. evanescens developed to the pupal stage at 36 °C, no adult emergence was observed at this temperature. Developmental periods were longer at 24 °C than at higher temperatures. The optimum age for T. evanescens to successfully parasitize host eggs ranged from 24 to 90 h. The parasitization frequency of the 56-78 h aged females was higher than for the other age groups. The daily egg laying pattern of female T. evanescens adults was similar when they were reared on Ephestia kuehniella or Plodia interpunctella eggs. Gamma- or ultraviolet-irradiated and unirradiated host eggs were equally preferred by adult females.     

The inhibitory potential of feed supplementation with rosemary and/or α-tocopheryl acetate on microbial growth and lipid oxidation of turkey breast during refrigerated storage

Twenty-four 12-week-old female turkeys divided into four equal groups were fed a basal diet (CONT) or basal diet supplemented with 300 mg α-tocopheryl acetate/kg (TOC), or 5 g rosemary/kg (ROS5), or 10 g rosemary/kg (ROS10), for 4 weeks. Following slaughter, fillets from breast were stored at 4 °C in the dark for 12 days, and lipid oxidation was assessed on the basis of the malondialdehyde formed, whereas microbial growth on the basis of total viable counts (TVC), lactic acid bacteria (LAB), Enterobacteriaceae (ENB) and psychrotrophic (PSY) bacteria. Results showed that incorporation of dried rosemary in turkey diets delayed lipid oxidation in raw breast meat during refrigerated storage. Dietary rosemary at the level of 1 g/100 g was significantly (P<0.05) more effective in delaying lipid oxidation compared to 0.5 g/100 g but inferior to the dietary supplementation of 300 mg α-tocopheryl acetate/kg. TVC, LAB, ENB and PSY bacterial counts were all significantly increased (P<0.05) in breast samples of all groups throughout the refrigerated storage. The TOC and CONT groups presented TVC, LAB, ENB and PSY counts that did not differ (P>0.05) among each other, during the whole storage period. However, the rosemary-supplemented groups presented bacterial counts that were significantly lower (P<0.05) than the CONT and TOC groups, at day 2 of storage period and thereafter. During this period, the ROS5 group presented TVC, LAB, ENB and PSY counts that were significantly higher (P<0.05) than the ROS10 group.     

Changes of radical-scavenging capacity and ferrous reducing power in chub mackerel Scomber japonicus and Pacific saury Cololabis saira during 4 °C storage and retorting

To clarify the effects of freshness of raw fishes and boil-retort process on the antioxidant activities, we determined stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity and ferrous reducing power in the ethanol extract solution of chub mackerel Scomber japonicus and Pacific saury Cololabis saira meat before and after retort process (115 °C for 80 min). The antioxidant activities in boiled (mizu-ni) and canned fish were also investigated. The mizu-ni can products contain only fish meat and little salt. The radical-scavenging capacity was increased about ten times in chub mackerel and about six times in Pacific saury by the retort treatment. Both antioxidant activities of raw chub mackerel meat increased during 10 days storage at 4 °C. On the other hand, the increasing of antioxidant activity in the stored and retorted meat was observed until four days storage. In the case of mizu-ni canned products, the antioxidant activities were high in common-grade cans rather than high-grade cans. Almost the antioxidant activities shown in this study were correlated with absorbance at 245 nm. We consider that the results about differences of antioxidant activities between raw and retorted fishes or fresh and several day stored fishes are useful for the food functions and safeties.     

Temperature induced denaturation of myosin: Evidence of structural alterations of myosin subfragment-1

Denaturation of myofibrillar proteins in porcine longissimus thoracis et lumborum muscle was investigated after pre-rigor temperature incubation at 20, 30 and 40 °C. At 24 h myofibrils were isolated and myosin was further cleaved by chymotrypsin. High temperature pre-rigor induced release of myosin S1 (subfragment-1), less (P < 0.05) Ca²⁺-ATPase activity and structural alterations of the region of the myosin molecule that harbors S1. Surface hydrophobicity of myofibrils from the 40 °C group increased (P < 0.001), suggesting a temperature-induced structural rearrangement exposing hydrophobic groups on the surface of myofibrils which in turn may explain the reduced water-holding of PSE meat.     

Production of n − 3 polyunsaturated fatty acid concentrate from sardine oil by lipase-catalyzed hydrolysis

The production of n − 3 polyunsaturated fatty acids (n − 3 PUFAs) concentrate from oil extracted from Pacific sardines (Sardinops sagax) was studied using lipase-catalyzed hydrolysis. Commercially available microbial lipases, from Candida Rugosa (CR), Candida cylindracea (CC), Mucor javanicus (MJ), and Aspergillus niger (AN) were used for enzymatic hydrolyses with extracted sardine oil, run at 37 °C with constant stirring for 1.5, 3, 6, and 9 h. Fatty acid composition analysis by gas chromatography showed that the refined unhydrolyzed oil contained 26.86% of eicosapentaenoic acid (EPA) and 13.62% of docosahexaenoic acid (DHA) (wt/wt%). CR lipase was the most effective in concentrating n − 3 PUFA. Hydrolysis with 250 U CR lipase increased EPA concentration to a relatively constant level of 33.74% after 1.5 h. DHA levels were also significantly increased from 13.62% to 29.94% with 500 U after 9 h. Compared to CR and CC lipases, MJ and AN lipases resulted in low n − 3 PUFA concentration. Triacylglycerol levels decreased significantly as reaction time progressed.     

Sensory,physical, chemical and microbiological changes in aquacultured meagre (Argyrosomus regius) fillets during ice storage

Commercial-sized meagre fillets were stored on ice at 4 °C for 18 days, in order to evaluate the loss of quality and freshness that occurs over this period of time. Physicochemical (pH, thiobarbituric acid (TBA), total volatile basic nitrogen (TVBN), trimethylamine (TMA), water activity, water-holding capacity, colour, texture and fatty acid profile), sensory and microbiological analyses were carried out at 0, 4, 7, 11, 14 and 18 days of storage. As part of the sensory analysis, attributes associated with fillet appearance, odour and texture were examined. Variations in pH, TBA, TVBN and TMA were observed throughout the storage period, although only TBA displayed a significant correlation with time (r = 0.96). L^∗ and b^∗ values increased, and the chroma and hue values decreased, reflecting the colour changes experienced by the fillets over time. With regards to the texture profile, hardness was significantly correlated with time (−0.68). All the sensory analysis attributes exhibited significant variations and correlations close to 1.00 with storage time, which is a reflection of the fillets’ loss of freshness. The correlation coefficients between aerobic mesophilic and psychrophilic bacteria, enterobacteria and coliform counts on the one hand and storage time on the other were also very high (0.99–1.00). A regression analysis using the acceptability limit set by the ICMSF standard (1986) for total aerobic mesophilic counts (7 log cfu/g) yielded a shelf-life for meagre fillets of 9 days. The TBA, sensory and microbiological analyses displayed very strong correlations with storage time, and they may be considered suitable indicators for evaluating meagre fillet spoilage during refrigerated storage.     

Efficacy of bacteriophage LISTEXP100 combined with chemical antimicrobials in reducing Listeria monocytogenes in cooked turkey and roast beef

The aim of this study was to verify the effectiveness of the commercially available anti-Listeria phage preparation LISTEX^™P100 in reducing Listeria monocytogenes on ready-to-eat (RTE) roast beef and cooked turkey in the presence or absence of the chemical antimicrobials potassium lactate (PL) and sodium diacetate (SD). Sliced RTE meat cores at 4 and 10 °C were inoculated with cold-adapted L. monocytogenes to result in a surface contamination level of 10³ CFU/cm². LISTEX^TMP100 was applied at 10⁷ PFU/cm² and samples taken at regular time intervals during the RTE product's shelf life to enumerate viable L. monocytogenes. LISTEX^™P100 was effective during incubation at 4 °C with initial reductions of L. monocytogenes of 2.1 log₁₀ CFU/cm² and 1.7 log₁₀ CFU/cm², respectively, for cooked turkey and roast beef without chemical antimicrobials (there was no significant difference to the initial L. monocytogenes reductions in the presence of LISTEX^TMP100 for cooked turkey containing PL and roast beef containing SD-PL). In the samples containing no chemical antimicrobials, the presence of phage resulted in lower L. monocytogenes numbers, relative to the untreated control, of about 2 log CFU/cm² over a 28-day storage period at 4 °C. An initial L. monocytogenes cell reduction of 1.5 log₁₀ CFU/cm² and 1.7 log₁₀ CFU/cm², respectively, for cooked turkey and roast beef containing no chemical antimicrobials was achieved by the phage at 10 °C (abusive temperature). At this temperature, the L. monocytogenes cell numbers of samples treated with LISTEX™ P100 remained below those of the untreated control only during the first 14 days of the experiment for roast beef samples with and without antimicrobials. On day 28, the L. monocytogenes numbers on samples containing chemical antimicrobials and treated with LISTEX^TMP100 stored at 4 and 10 °C were 4.5 log₁₀ CFU/cm² and 7.5 log₁₀ CFU/cm², respectively, for cooked turkey, and 1.2 log₁₀ CFU/cm² and 7.2 log₁₀ CFU/cm², respectively, for roast beef. In both cooked turkey samples with and without chemical antimicrobials stored at 10 °C, the phage-treated samples had significantly lower numbers of L. monocytogenes when compared to the untreated controls throughout the 28-day storage period (P < 0.0001). For roast beef and cooked turkey containing chemical antimicrobials treated with LISTEX^TMP100 and stored at 4 °C, no more than a 2 log CFU/cm² increase of L. monocytogenes was observed throughout the stated shelf life of the product. This study shows that LISTEX^™P100 causes an initial reduction of L. monocytogenes numbers and can serve as an additional hurdle to enhance the safety of RTE meats when used in combination with chemical antimicrobials.     

Influence of storage temperature and duration on lipid and protein oxidation and flavour changes in frozen pork dumpling filler

This study was conducted to evaluate the effect of storage temperature and duration on oxidation and flavour changes in frozen pork dumpling filler. Freshly prepared dumplings were stored for 0, 30, 60, 90, and 180 d at − 7 °C, − 18 °C, and an oscillation between − 7 °C and − 18 °C. The samples stored at − 7 °C for 180 d had significantly higher levels of TBARS and protein carbonyls than those stored at − 18 °C and the fluctuating − 7 °C/− 18 °C (P < 0.05). The percentage of unsaturated fatty acids in total lipids decreased with extended storage times. The volatile compounds with pleasant odours decreased with time, while the compounds with pungent tastes and smells increased (P < 0.05). The sensory results showed that the dumplings stored at higher frozen temperatures for long periods of time had significantly lower acceptability scores (P < 0.05). The results suggest that oxidation is a primary cause of quality deterioration in pork dumpling filler during frozen storage.