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.     

Oxidation stability of the lipid fraction in milk powder formulas

The purpose of this study was to predict the shelf life of distinct milk powder formulas by measuring hydroperoxides, headspace volatile compounds (propanal, pentanal and hexanal), fatty acid content, and sensory quality. The oxidation stability of three formulas was followed over 15 months of storage at 25 and 37 °C. These formulas were a non-supplemented formula (NSF), and two formulas supplemented with n − 3 and n − 6 long-chain polyunsaturated fatty acids, a formula with 0.83 and 0.47% (SFA), and one with 27.8 and 3.51% of n − 3 and n − 6 long-chain polyunsaturated fatty acids (SFB), respectively. Relative stability decreased in the order NSF at 25 °C > SFA at 25 °C ? SFA at 37 °C ? SFB at 25 °C > SFB at 37 °C. Therefore, we conclude that the polyunsaturated fatty acid content, storage temperature and storage time are very important factors for determining the oxidation stability.     

The Microbial and Sensory Quality of Mackerel Hot Smoked in Mild Conditions

The quality indices of Atlantic mackerel, hot smoked at core temperature not exceeding 60°C, containing 14-27 g salt and 580-670 g water per kg meat, was determined just after smoking and during storage. The aerobic plate count after smoking, chilling and packing in cardboard boxes was 0-12 cfu/25 cm²of the skin of the smoked fish and 10-240 cfu/g of flesh. It was 1.9 log cycle lower than that in the frozen raw material. At 2°C, the bacterial count on the fish surface and in the meat remained unchanged for at least 3 wk. At 8°C after 14 d, the cfu in the meat of smoked fish ranged from 1.8×10²to 1.6×10⁷/g. The total count on the skin and just under the skin did not increase up to 21 d at 2 and 8°C. There was no statistically significant difference between the mean values of all evaluated sensory attributes of the smoked fish stored up to 2 wk at 2 and 8°C. These results regard products from a smoking plant of very high hygienic standard, fulfilling all EC requirements, with quality assurance system based on HACCP.     

The effects of colorifico on lipid oxidation,colour and vitamin E in raw and grilled chicken patties during frozen storage

Colorifico is a spice consisting essentially of a mixture of annatto (Bixa orellana) and corn flour. The effects of colorifico addition (0.4 g/100 g) to chicken meat on the development of lipid oxidation, colour stability, and degradation of bixin and vitamin E was investigated in raw and grilled patties during storage at −18 °C for 120 days. Colorifico was able to provide a more stable and intense red and yellow colour in both raw and grilled chicken patties when compared to the meat without spice. Lipid oxidation was delayed by colorifico in the grilled patties until 30 days of storage; however, no effect was observed in the raw patties. Vitamin E content was significantly higher in raw meat with colorifico and heat treatment resulted in relatively less loss when compared to the meat without spice; however, during storage both presented the same degradation pattern. Bixin content was stable during storage but not after grilling. The observed antioxidant mechanism suggests that vitamin E, probably the tocotrienols, is acting along with bixin to protect the unsaturated lipids from oxidation.     

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.     

Nutritional and sensory aspects of light lamb meat enriched in n−3 fatty acids during refrigerated storage

Fatty acid content and sensory characteristics of meat from light lambs fed three diets supplemented with different sources of n−3 fatty acids (fish oil, extruded linseed and extruded linseed plus microalgae) and a control diet during refrigerated storage have been studied. The meat from lambs fed linseed diets had the highest levels of C18:3 n−3, while animals fed fish oil had the highest long-chain n−3 polyunsaturated fatty acids (PUFA). Thus, 100 g of meat from lamb fed the fish oil diet provided 183 mg of long-chain n−3 PUFA, representing 40% of the daily recommended intake. The levels of n−3, n−6 and long-chain n−3 PUFA decreased during a 7-day storage period. The meat from lambs fed the fish oil diet had high scores of fish odour and flavour and rancid odour and flavour and the lowest overall liking. Rancid odour and flavour increased after storage, mainly in supplemented groups.     

Quality of superchilled vacuum packed Atlantic salmon (Salmo salar) fillets stored at −1.4 and −3.6 °C

The most important factor for increasing shelf life is the product temperature, and since fish is more highly perishable than meat, the temperature is even more important. In the present study, portions of fillets of farmed Atlantic salmon (Salmo salar) were superchilled at two temperature levels, −1.4 and −3.6 °C. Texture, drip loss, liquid loss, cathepsin activities and protein extractability were investigated during storage and compared to ice chilled and frozen references. Drip loss was not a major problem in superchilled salmon. Textural hardness was significantly higher in superchilled salmon fillets stored at −3.6 °C compared to those stored at −1.4 °C, ice chilled and frozen references. Cathepsins B and B + L were not deactivated at the selected storage temperatures. The storage time of vacuum packed salmon fillets can be doubled by superchilled storage at −1.4 °C and −3.6 °C compared to ice chilled storage.     

Fish oil in feeds for entire male and female pigs: Changes in muscle fatty acid composition and stability of sensory quality

A total of 72 crossbred [(Norwegian Landrace × Yorkshire) × Duroc] male and female growing-finishing pigs were restrictedly fed diets containing fish oil to study the fatty acid composition of Musculus longissimusdorsi and sensory quality of belly and neck. Six diets were used: two low-fat diets with or without 0.5% fish oil added, and four medium-fat diets with palm kernel oil to fish oil in ratios given as % inclusion: 4.1:0.0, 3.9:0.3, 3.6:0.5 and 3.4:0.7. Feeding fish oil gave a dose-dependent response between fatty acids in the diets and in the M.longissimusdorsi and increased the level of very long chain n−3 fatty acids, especially the C22:5n−3 (DPA). A more efficient n−3 fatty acids deposition was obtained when given as a medium-fat diet rather than the low-fat diet. Female pigs had a significant higher percentage of monounsaturated fatty acids and C18:1 than males suggesting a gender related difference in the delta-9-desaturase activity. No significant differences were found in sensory attributes for short-term stored neck and belly. For pigs fed the highest level of fish oil (0.7%) long-term stored (12 months at −80 °C, 6 months at −20 °C) belly showed a slight increase in fish oil flavour. After warmed-over treatment, fish oil odour and flavour as well as rancid flavour were increased in this group. The results suggest levels of dietary fish oil up to 0.5% produce a healthier meat fatty acid composition, without negative effects on sensory attributes, even in long-termed stored belly.     

The effect of α-tocopherol on the oxidation of mackerel oil

Mackerel oil is prone to autooxidation because it has a high content of polyunsaturated fatty acids. Antioxidants therefore have to be added to the oil to control oxidation during processing. The effect of 50, 100, 250 and 500 parts per million (ppm) concentrations of α-tocopherol on the oxidation of unrefined mackerel oil samples (recovered by solvent extraction), was investigated at 30, 4 and −40 °C over a period of 66 days by monitoring changes in peroxide values, conjugated diene content as well as levels of thiobarbituric acid reactive substances. There were significant differences (P < 0.05) between treated and control samples at all the temperatures investigated for all the α-tocopherol concentrations over the storage period. Higher concentrations of α-tocopherol, i.e., 250 and 500 ppm were less effective in controlling oxidation in the oils than lower α-tocopherol levels (50 and 100 ppm). Oxidation was minimal at low temperatures as inferred from the methods used to assess autooxidation. Treatment of mackerel oil with 50 or 100 ppm α-tocopherol at −40 °C produced the lowest oxidation over the 66-day period and was considered as adequate levels of incorporation in crude mackerel oil to minimize oxidation. There was no significant difference (P > 0.05) between the effects of 50 and 100 ppm of α-tocopherol after 66 days. Fifty ppm of α-tocopherol is therefore regarded as the preferred concentration for controlling oxidation of mackerel oil on the basis of cost and efficacy.     

Effect of cooking methods on fatty acids,conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat

The effect of boiling, microwaving and grilling on the composition and nutritional quality of beef intramuscular fat from cattle fed with two diets was investigated. Longissimus lumborum muscle from 15 Alentejano young bulls fed on concentrate or pasture was analyzed. Cooking losses and, consequently, total lipids, increased directly with the cooking time and internal temperature reached by meat (microwaving > boiling > grilling). The major changes in fatty acid composition, which implicated 16 out of 34 fatty acids, resulted in higher percentages in cooked beef of SFA and MUFA and lower proportions of PUFA, relative to raw meat, while conjugated linoleic acid (CLA) isomers revealed a great stability to thermal processes. Heating decreased the PUFA/SFA ratio of meat but did not change its n−6/n−3 index. Thermal procedures induced only slight oxidative changes in meat immediately after treatment but hardly affected the true retention values of its individual fatty acids (72–168%), including CLA isomers (81–128%).     

Effects of different sources of fat (calcium soap of palm oil vs. extruded linseed) in lactating ewes' diet on the fatty acid profile of their suckling lambs

The main objective of this study was to evaluate the effects of supplementing lactating ewe diets with extruded linseed on the fatty acid (FA) composition of intramuscular and subcutaneous fat depots of suckling lambs. Twenty-four pregnant Churra ewes were divided into two groups based on the milk production, age, body weight and parity, and assigned to one of two treatments. Each ewe of the Control treatment was supplemented with 70 g/day of FAs from a calcium soap of palm oil, while the other treatment group (Lin) was supplemented with 128 g/day of extruded linseed. All lambs were reared exclusively on milk and were slaughtered when they reached 11 kg live weight. FA profiles of ewe milk, lamb meat and subcutaneous adipose tissue were determined by GC. Lamb performance was not affected by the treatments. Muscle fat and adipose tissue from the Lin treatment showed higher proportions of polyunsaturated fatty acids (PUFA). The percentages of α-linolenic (C18:3 n − 3), docosahexaenoic (C22:6 n − 3), vaccenic (trans-11 C18:1) and rumenic (cis-9, trans-11 C18:2) acids in both fat depots were higher in Lin than in Control suckling lambs. Furthermore, meat fat from Lin carcasses displayed a lower n − 6/n − 3 ratio than Control samples. Intramuscular depots clearly showed a greater content of PUFA, including cis-9, trans-11 C18:2, and a lower n − 6/n − 3 ratio than subcutaneous fat. The results from this study demonstrate that dietary extruded linseed supplementation of lactating ewes enhances the nutritional quality of suckling lamb fat depots such as intramuscular and subcutaneous fats.     

The effect of liquid smoking of fillets of trout (Salmo gairdnerii) on sensory,microbiological and chemical changes during chilled storage

The storage time at 4 ± 1 °C of liquid smoked fillets of trout (Salmo gairdnerii) produced with a new smoking technique, using a combination of liquid smoke and steaming at 2 bar pressure for 30, 45 and 60 min, was studied. Maximum total viable counts (TVC) were reached after 25 days in the samples processed for 30 min and after 48 days in those processed for 45 and 60 min. However, panellists rejected the samples long after maximum TVC was observed. The increase of TVC was also confirmed using a particle size analyser, indicating a possible direct detection of microbial growth. A reduction of about 50% in the C22:6n − 3/C16:0 ratio was found across the whole period of storage, indicating lipid oxidation. The hypoxanthine/inosine (Hx/Ino) ratio showed a good relationship with both TVC and sensory results. Thus, when the Hx/Ino ratio was higher than 1.3, the products had reached their maximum acceptable TVC and were approaching their rejection time by the panellists, indicating that the Hx/Ino ratio is a good indicator of the shelf-life of smoked products of trout (S. gairdnerii).     

Effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken meat

This study examined the effects of freezing temperature and duration of frozen storage on lipid and protein oxidation in chicken leg and breast meat. The meat was frozen at three different temperatures (−7, −12 and −18 °C) and then stored at −18 °C for up to 6 months. A significant effect of frozen storage duration on lipid oxidation was detected in leg and breast meat, whereas freezing temperature had no significant effect. In leg meat, freezing at −7 °C had a significant impact on protein oxidation, measured as the increase in carbonyl groups and the decrease in total sulphydryl groups, after 3 months of frozen storage. Lipid and protein oxidation appeared to occur simultaneously in chicken meat during frozen storage and was more intense in leg meat than in breast meat.     

The Effect of Fluctuating vs. Constant Frozen Storage Temperature Regimes on Some Quality Parameters of Selected Food Products

Samples of frozen raw salmon, smoked mackerel, stewed pork pieces, ice cream, pizza (with a mozzarella cheese topping), hollandaise sauce, strawberries, and blanched broccoli were mildly temperature abused by subjecting them to temperature fluctuations below the freezing point. This involved three temperature fluctuation cycles of −30 °C to −10 °C to −30 °C on consecutive weeks followed by storage at a constant −30 °C for 8 mo. The samples were compared with duplicate sets held for 8 mo at a constant −60 °C (superfreezing) or −30 °C (control) and testing (objective and sensory) was conducted after 0, 1, 2, 4 and 8 mo. The temperature regimes had a larger effect on peroxide (PV) and free fatty acid (FFA) values than on any of the other parameters tested over the product range. The pattern in the data was the same for each fat-containing product in that superfreezing (−60 °C) gave the lowest PVs and FFAs, the control (−30 °C) was intermediate, while the fluctuating regime gave the highest values. PVs and FFAs also increased with length of time in frozen storage. While smoked mackerel had relatively high PVs and FFAs, rancidity was not a major problem in any of the fat-containing products as indicated by sensory tests. The temperature regimes had a minimal effect on texture, colour, water-holding capacity and drip loss on thawing for most of the products. However, superfreezing resulted in a better retention of vitamin C in strawberries.     

Volatile compounds and fatty acid profiles in commercial milk-based infant formulae by static headspace gas chromatography: Evolution after opening the packet

The evolution of the volatile compounds propanal, pentanal and hexanal, and fatty acid profiles were examined in 20 infant formula (IF) milk powders during storage at 25 °C for 70 days after their packaging was opened. Few changes were observed in the fatty acid content during storage, but significant losses were found in C18:2 n − 6 and C18:3 n − 3 for some formulae. All three volatiles increased during storage in all formulae, confirming oxidative stability decreases once packets were opened. Significant correlation (p < 0.05) was detected between hexanal content and oxidation of n − 6 PUFA, specifically C18:2 n − 6 losses, and between propanal content and oxidation of n − 3 PUFA, specifically from C18:3 n − 3 losses.     

Effects of skin and grilling method on formation of heterocyclic amines in chicken pectoralis superficialis muscle

Mutagenic heterocyclic amines (HAs) originate in processed proteinaceous foods. The effects of the presence of skin (with vs. without) and of grilling method (two plate vs. infrared) on the content of HAs in grilled chicken pectoralis superficialis muscle (temperature, 220 °C) were investigated. HA precursors (creatine, creatinine, free amino acids and carbohydrates) and HAs of these raw and grilled breast muscles were determined. The muscles originated from 24 birds of either sex (provenance Ross; aged 40-45 days). The HA content was determined in homogenates of the upper and lower surface slices of the grilled muscles (T_i = 82 °C). A higher content of total free amino acids was seen for the muscle (27.1 mmol kg⁻¹ raw meat) than for the skin (21.7 mmol kg⁻¹ raw meat). The creatine, creatinine and carbohydrate levels in the skin were below the limits of detection. The contents of creatine (31.8-38.7 mmol kg⁻¹) and creatinine (0.24-0.33 mmol kg⁻¹) in the breast muscle were determined. Relatively high levels were seen for glucose (23 mmol kg⁻¹ raw meat) and fructose (10 mmol kg⁻¹ raw meat) in the muscle, with other sugars present at low levels (<2 mmol kg⁻¹ raw meat). For the chicken muscle grilled on a two-plate grill, the contents of total HAs (PhIP, MeIQx, DiMeIQx, Harman and Norharman) were lower with the skin in place than in the muscle grilled without the skin (3.5 μg kg⁻¹vs. 4.8 μg kg⁻¹). Also, during infrared grilling with the skin, lower amounts of HAs were formed than with grilling on the two-plate grill (2.4 μg kg⁻¹vs. 3.5 μg kg⁻¹). On average, the infrared-grilled samples with skin contained 3-fold more total HAs than similar samples without the skin (2.4 μg kg⁻¹vs. 0.8 μg kg⁻¹), with the highest levels seen for PhIP and MeIQx.     

Effect of freezing on the physicochemical, textural and sensorial characteristics of salmon (Salmo salar) smoked with a liquid smoke flavouring

This study reports the effect of different refrigeration/freezing treatments on the physicochemical, textural and sensorial properties of farmed Atlantic salmon (Salmo salar) treated with a commercial liquid smoke flavouring. Observations were made on three groups of fillets - group RFS: salted, smoked and stored at 4 °C; group BFS: frozen at −25 °C for 24 h, thawed, salted, smoked and stored at 4 °C; and group AFS: salted, smoked and frozen at −25 °C for 24 h and stored at −18 °C - over a period of 45 days. Scores (on a scale of 1-9) were provided for different sensorial attributes by a panel of 10 trained tasters. Sixty percent of the panellists consistently preferred the AFS fillets. The maximum shelf life associated with each treatment was defined as the last sampling day on which a mean score of ≤5 was awarded for the fillet sensorial attributes by ≥50% of the panellists. Freezing the salmon for 24 h before smoking (BFS) did not increase its shelf life (30 days) over that of refrigerated smoked salmon (RFS). In addition, the former treatment had a negative effect on the adhesiveness, cohesiveness, smoke odour intensity and colour intensity of the flesh. However, maintaining the fish frozen at −18 °C (AFS) increased its shelf life (>45 days) and invested the flesh with greater firmness, cohesiveness and colour intensity.     

Effect of cold storage on vitamins C and E and fatty acids in human milk

Vitamins C and E and fatty acid levels in human milk were determined when fresh, after refrigeration at 4 °C for 96 h, and after freezing at −20 °C or −80 °C for 12 months. Total vitamin C content at 4 °C (6 h), −20 °C (8 months) and −80 °C (12 months) was significantly decreased. Vitamin E levels did not change at either refrigeration temperature (under 24 h) or at freezing or ultrafreezing temperatures. Our analysis revealed that fatty acids are not affected by cold storage. In conclusion, we recommend a change in milk storage practices; specifically, it should be stored up to 3 h in a refrigerator, up to 5 months in a freezer or up to 8 months in an ultrafreezer (−80 °C). Alternatively, vitamin C supplementation may be considered. In addition, we propose vitamin C as a marker for human milk stability.     

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.