Lipolysis and Oxidation in Ultra‐High Temperature Milk Depend on Sampling Month,Storage Duration,and Temperature

During storage, some factors (for example, storage duration and temperature) can affect milk stability and consumer acceptability. Thiobarbituric acid reactive substances (TBARSs), lipid classes, and fatty acid profiles in stored ultra‐high temperature (UHT) milk were analyzed to assess the effects of storage time and temperature on lipid oxidation and lipolysis. With storage duration up to 12 months, the milk fat phase was separated and showed high levels of oxidation and lipolysis, manifested as increased levels of TBARS and free fatty acids. High oxidation levels decreased the percentage of unsaturated fatty acids (UFAs) in triacylglycerol and phospholipids. Higher storage temperatures (20, 30, and 37 °C) resulted in a higher degree of fat aggregation, oxidation, and lipolysis compared with refrigerated storage (4 °C). Additionally, sampling month of raw milk (May, July, and November) affected the lipid profiles of UHT milk during storage, with more UFA oxidized in July than in the other 2 months.     

Measurement of lipid oxidation and porphyrins in high oxygen modified atmosphere and vacuum-packed minced turkey and pork meat by fluorescence spectra and images

This paper illustrates that fluorescence spectroscopy and imaging can be used to measure the extent and distribution of lipid oxidation in meat. Minced turkey thighs and pork semimembranosus muscles were stored for 7 and 12 days at 4°C in high oxygen (O(2)) modified atmosphere packages and vacuum. Turkey meat packed in high O(2) atmosphere was oxidised already after 7 days of storage. The sensory rancid odour score was 4.7 (on a scale from 1 to 9) and the TBARS value was 1.86mg MDA/kg. There was also an increase in fluorescence emission intensity in the 410-550nm region, which arises from lipid oxidation products. The combination of unsaturated fatty acids and access to O(2) resulted in lipid oxidation gradients in the turkey meat samples, and these gradients were clearly visualised by fluorescence images. In comparison, pork meat was more stable against lipid oxidation, with TBARS values <0.2mg MDA/kg and no development of fluorescent lipid oxidation products was detected. The fluorescence spectra measured in the present experiment suggest that turkey thighs and pork semimembranosus muscle in addition to protoporphyrin also have a natural content of Zn protoporphyrin. The porphyrin content was higher in pork meat than in turkey meat. It increased during storage time when the meat was packed in vacuum, and it decreased with O(2) availability. The distribution of porphyrins in the meat was visualised by fluorescence imaging.     

The effect of oxygen exclusion during cooling of cooked turkey breast on the development of lipid oxidation in the stored product

In this study it was shown that cooling of freshly cooked turkey breast out of contact with air was highly effective in reducing the subsequent progress of lipid oxidation in the stored chilled (4 °C) product. Compared with cooling in contact with air, lipid oxidation in aerobically stored samples, as measured by muscle concentrations of hexanal and 2‐thiobarbituric acid‐reactive substances, was much lower for breast portions which were either cooled in a nitrogen atmosphere or subjected to hot vacuum packaging. Tissue hexanal concentrations of around 1.4 µg g^?1 muscle, which have previously been shown to be associated with the initial stages of sensory detection of oxidised off‐flavours, were reached after 5 and 3 days of storage respectively in nitrogen‐cooled/air‐stored and vacuum‐packed/air‐stored samples compared to only 1 day in breast portions which were cooled and stored in air. Cooling and storing under nitrogen had the effect of almost completely inhibiting lipid oxidation in samples stored for 7 days. An acceptable flavour shelf‐life of approximately 7 days with respect to lipid oxidation was achieved when vacuum‐packed breast portions cooked to an internal temperature of 85 °C were packaged before the core temperature fell below about 60 °C. © 2002 Society of Chemical Industry     

Effect of high-pressure treatment on lipid oxidation in turkey thigh muscle during chill storage

 Formation of secondary lipid oxidation products during chill storage of vacuum-packed (99% vacuum), pressure-treated turkey thigh muscle was found to depend on working pressure (pressure range up to 500 MPa at 10°C) and to a lesser degree on pressurization time (10 and 30 min). Pressure treatment at 400 MPa and lower pressures for 30 min (and for 10 min) resulted in less formation of thiobarbituric-acid-reactive substances (TBARS) during 6 days of storage at 5°C compared to heat treatment at 100°C for 10 min, while pressure treatment at 500 MPa for 30 min gave similar development of TBARS as did the heat treatment. The formation of TBARS during storage at 5°C was found to depend exponentially on the pressure used for treatment at both 10 min and 30 min, and apparent volumes of activation are proposed as a parameter for quantification of the effects of pressure on lipid oxidation in meat during subsequent storage. Received: 18 November 1996     

Changes in the lipids of turkey muscle during storage at chilling and freezing temperatures

Diced turkey leg and breast muscle stored for 22 days at 0° and —3°, and for up to one year at —10°, —20° and —60° was examined at intervals for lipid composition. Free fatty acids increased at all temperatures except —60°, with a Q₁₀ of 3-4 between 0° and —20° 90% of the fatty acids liberated were unsaturated, matching in composition the unsaturated acids of the muscle glycerophospholipids. Demonstration of linear relationships between increase in free fatty acids and decrease in phosphatidylethanolamine or increase in lysophosphatidylcholine confirmed phospholipase A₂ as the enzyme mainly responsible. The composition of the fatty acids liberated during storage at 0° and —3° showed that both lipase and phospholipase were active. A slight decrease in extractability, resulting in an apparent loss of phospholipid-P, was observed after storage at low temperatures.     

Residual glutamic-oxaloacetic transaminase (GOT) activity in thermally processed poultry and poultry products as an indicator of end-point temperatures

Glutamic-oxaloacetic transaminase (GOT) activities in chicken and turkey thigh and breast meat samples, thermally processed at 60–84°C in a model heat-treating system, were evaluated for use as indicators of end-point cooking temperatures (EPT). Wings, breasts, thighs and legs from commercially cooked, whole, roasted chickens and commercially processed products containing chicken and turkey meat were analyzed also to determine if residual GOT activities would indicate compliance with recent FDA/FSIS EPT recommendations. Activities of samples processed in the model system decreased logarithmically with increasing temperatures. GOT activities were higher (P < 0·05) in thigh meat than breast meat in both chicken and turkey samples; activities were higher in turkey than chicken. GOT values for chicken thigh and breast meat at 74°C, the FDA/FSIS recommended EPT for use by food handlers and retailers, were 735 and 164 Sigma-Frankel units ml^?1 (SFU ml^?1), respectively. Values for turkey thigh and breast meat at this temperature were 1080 and 450 SFU ml^?1, respectively. The range of activities was 7–13 SFU ml^?1 in commercially prepared chicken products and 27–161 SFU ml^?1 in turkey products. Analysis of these products showed adequate cooking and compliance with FDA/FSIS recommended EPT for retail sale. These data indicate that residual GOT activity in processed poultry has potential for use as an indicator of EPT.     

Effect of some factors used to the chicken meat preservation and processing on the protease activity

The obtained results indicated that the cathepsin activity was higher by about 60% in the extract from thigh than from breast muscles. Freezing and defrosting (not stored) of chicken meat did not influence the breast muscle cathepsin activity while they caused a decrease of activity of about 20% in the case of thigh muscles. The increase in cathepsin activity was noticed in both kinds of muscles during storage at ?20 °C up to 4 months (45.6% and 19.4% for thigh and breast muscles respectively). The activity of cathepsin in extract from 5 months stored meat reached 80% in case of breast muscles and 83% in case of thigh muscles in relation to control sample respectively. The cathepsin activity significantly increased during heating of breast muscles up to 60 °C, but in case of thigh muscles it was slightly higher than at 50 °C. The heating of cured chicken breast muscles up to 60 °C caused a non significant growth in cathepsin activity opposite to raw muscles. The cathepsin activity from all cured samples heated up to 70 °C were several times lower in relation to control samples. The cathepsin activity of both thigh and breast muscles were resistant to gamma radiation. The investigated factors caused changes in the activity of cathepsin but none of them caused its total inactivation. The changes of cathepsin activity depended on the kind of muscles and the kind and the value of acting factors.     

Lipid stability in powdered infant formula stored at ambient temperatures

Lipid stability of standard infant formula was evaluated at ambient temperatures, namely 25, 30 and 37 °C, during 3 months. Lipids were thoroughly analysed to evaluate changes in fatty acid composition and trans fatty acid isomers, non‐volatile oxidation compounds including oxidised, dimeric and polymeric triacylglycerols, and tocopherol. No significant changes in either of the parameters examined were found in total lipids extracted from infant formula along the storage period. However, the minor free oil fractions (about 7.5% of total lipids) showed a significant increase in oxidation compounds and marked decrease in tocopherol levels during storage at all temperatures. Samples stored at 37 °C for 3 months were rancid and, accordingly, contained the highest oxidation level in the free oil fraction, whereas total lipids extracted were apparently not oxidised. Results showed the necessity of analysing separately the free oil fraction in infant formulae to obtain a clear picture of the oxidation status.     

Influence of the oxidative quality of dietary oil on broiler meat storage stability

Broilers were fed a high fat diet containing 11% oil (9% rapeseed oil, 2% soya bean oil) and the oil was given either as fresh (peroxide value of 1 meqv. O₂kg⁻¹ oil) or as highly oxidised (peroxide value of 156 meqv. O₂kg⁻¹ oil). Diets were supplemented with 46 mg all-rac--tocopheryl acetate kg⁻¹ diet, resulting in a tocopherol content of 80.8 mg -tocopherol and 58.6 mg γ-tocopherol per kg diet in the fresh oil diet and of 44.0 mg -tocopherol and 18.3 mg γ-tocopherol per kg diet in the oxidised oil diet, respectively, reflecting the degradation of the natural occurring tocopherols in the oxidised diet. Only minor differences were seen with respect to fatty acid composition in muscles from birds fed the two diets. The oxidation of the dietary oil lowered lipid stability significantly (p < 0.01) in both raw and precooked meats during chill storage, whereas only minor effects on the stability of frozen meat were seen. Tocopherol levels were significantly lower (p < 0.01) in muscles from birds fed the oxidised oil diet, explaining the decreased lipid stability of meat from these birds. Thigh meat was more susceptible to lipid oxidation during storage than breast meat, regardless of dietary treatment, although thigh meat had markedly higher tocopherol levels than breast meat. The molar ratio of PUFA > 18:2 (polyunsaturated fatty acids with three or more double bonds) to -tocopherol was significantly (p < 0.01) higher in thigh meat compared with breast meat, explaining the lower stability of the former during storage.     

Storage and Lipid Quality of Chunked, Formed Roasts Containing Mechanically Separated Lamb

Restructured chunked and formed roasts containing 10 or 30% mechanically separated lamb (MSL) were made with meat from ram or wether lambs. Roasts were either frozen immediately after formulation and stored at -30°C before cooking to 71°C, or precooked immediately to 63°C, chilled and reheated to 71°C before storage at 4 and -30°C. Storage periods varied depending upon treatment. Roasts with 10% MSL contained less total fat and less free fatty acids (FFA) than those with 30% MSL. There was little evidence of extensive lipid oxidation as measured by thiobarbituric acid values and peroxide oxygen values in any of the roasts. There was an indication that pre-cooking and curing prior to storage increased glycerolipid hydrolysis because of increased levels of FFA. Apparently increased hydrolysis occurred in triglycerides since levels of phospholipids did not change.     

Hydrolytic and Oxidative Changes in the Lipids of Chicken Breast and Thigh Muscles During Refrigerated Storage

The changes in free fatty acid (FFA) amount and composition and in Thiobarbituric acid reactive substances (TBARS) were simultaneously determined in chicken breast and thigh muscles at intervals between 1 and 14 d of storage at 4 °C (1, 3, 7, 10, 14). The rates of lipid hydrolysis were fast in the first 3 d and then slowed until day 14; phospholipids showed the same pattern but hydrolysis of triacylglycerols was linear at least in thigh muscles. Oxidation increased linearly during storage. Thigh muscles contained 3 times more FFAs than breast muscles and 2 to 4 times less TBARS suggesting that lipolysis did not favor lipid oxidation although both increased concomitantly.     

Antioxidant ability of broccoli flower buds during short-term storage

Some metabolic changes in broccoli heads stored under commonly-applied conditions were investigated. Freshly harvested broccoli of Lord cultivar were stored at 20°C and at 5°C for 3 and 7 days, respectively, either non-packaged or packaged in polymeric film samples. Short-term storage at room temperature induced accumulation of total phenols, especially in non-packaged broccoli. With low-temperature treatment, phenol content rose only after 7 day storage of non-packaged heads. Both low temperature and application of polymeric foil stopped losses of ascorbic acid. Total antioxidant activity increased considerably during storage in all treatments. Changes of fatty acids were manifested as a slight decrease in saturated fatty acids in cold storage and increase of polyunsaturated fatty acids in most treatments. Metabolism of fatty acids did not correspond to thiobarbituric acid-reactive substances (products of lipid peroxidation).     

Gelation of Turkey Breast and Thigh Myofibrils: Changes During Isolation of Myofibrils

The relationship between functional properties of meat and myofibrils was examined for turkey breast and thigh by determining gel-forming ability of proteins at each step in a myofibril isolation procedure. Physical properties of thermally induced gels (70°C for 30 min) were determined by torsional fracture analysis. Maximum shear stress (force) was obtained after removal of water-soluble components, whereas filtration was required to achieve maximum shear strain (deformability). Shear stress increased 150% and shear strain 59%. Changes in fracture properties were similar between meat types, and therefore, not the cause of meat type-associated differences in comminuted turkey.     

Antioxidant activities of defatted sesame meal extracts in cooked turkey breast and thigh meats

The antioxidant properties of methanolic extract of raw and roasted (at 200 °C for 60 min) defatted sesame‐meal in turkey breast and thigh meat systems were determined. The TBARS values of turkey breast and thigh meat added with 0.1% of roasted defatted sesame‐meal extract were 18.8% and 24.7%, respectively, lower than those of untreated controls after 5 days of storage. The turkey meats added with roasted defatted sesame‐meal extract had higher a* and b* values than those of controls due to the browning effects occurred in sesame seeds during roasting. The amounts of volatile hydrocarbons (pentane, hexane, heptane, and octane) and carbonyls (propanal, butanal, pentanal, hexanal and heptanal) significantly decreased by the addition of roasted defatted sesame‐meal extract. In particular, the amount of hexanal, the most predominant volatile compound in the cooked turkey meat, decreased by 74% and 83% in turkey breast and thigh meat, respectively. However, raw defatted sesame‐meal extract did not show significant antioxidant activity in turkey meats. These results indicated that heat treatment of sesame‐meal increased the antioxidant activities of methanolic extract of defatted sesame meal. Copyright © 2007 Society of Chemical Industry     

Cholesterol oxides in processed chicken muscle as influenced by dietary α-tocopherol supplementation

The effect of dietary α-tocopheryl acetate supplementation on the formation of cholesterol oxidation products (COPs) in chicken muscle during storage was investigated. Broiler chicks (Cobb 500 strain) were fed diets supplemented with 20, 200 or 800 mg α-tocopheryl acetate kg(-1) feed. Cooked breast and thigh muscle patties were prepared and stored at 4 °C for up to 12 days. Dietary supplementation significantly (p < 0.05) increased α-tocophenol concentrations in cooked muscle and decreased thiobarbituric acid-reacting substances (TBARS) during storage. COPs increased during storage. Total COPs ranged from 0.17-3.48 and 2.49-5.79 μg g(-1) in breast and thigh meat, respectively. TBARS and total COPs were linearly correlated in breast (r = 0.68, p < 0.001,) and thigh patties (r = 0.75, p < 0.05). Dietary α-tocopheryl acetate supplementation significantly (p < 0.05) reduced the formation of COPs during storage. Total COPs formed after 12 days were reduced by 42 and 75% in breast, and 50 and 72% in thigh, at supplementation levels of 200 and 800 mg kg(-1) feed, respectively.     

Changes in lipids of whole and minced rayfish (Raja clavata) muscle during frozen storage

The effects of the storage temperature (?18 °C and ?40 °C) and the addition of butylhydroxytoluene (BHT) on the different classes of lipids (phospholipids, triacylglycerides, free fatty acids, sterols and sterol esters plus waxes) and the fatty acid composition of minced (8 and 12 mm) and whole rayfish wing muscle stored for 1 year in the frozen state were studied. The phospholipid content decreased significantly and the free fatty acid content increased significantly at both storage temperatures, but more pronounced, at ?18 °C. Significant differences were found between phospholipid and free fatty acid contents of the minced and the whole samples, which again were more pronounced at ?18 °C. A significant increase of the major fatty acids (22∶: 6n-3 and 16:0) was observed after 1 year in the frozen state. Significant differences were also obtained between the samples stored at ?18 °C and at ?40 °C; the lower the storage temperature, the higher their content. The polyunsaturated fatty acid (PUFA) content increased significantly in all the samples. Significant differences were found between the samples stored at ?18°C and at ?40°C. The lower the temperature, the higher the PUFA content. Nonsignificant differences were observed between the 8-mm and the 12-mm minced samples. Non-significant differences were found between the samples stored in the presence and in the absence of BHT. Mincing hastened hydrolytic and oxidative processes, which were slowed down at the lower storage temperature. Nonetheless, nonsignificant differences were found between both particle sizes.     

9种腌腊肉制品贮存过程中游离脂肪酸的变化、影响因素及其来源途径的研究

选取9种腌腊肉制品,通过比较肥瘦质量比例、贮藏温度、不同产地、灭酶与不灭酶产品游离脂肪酸的含量及酸性脂肪水解酶、中性脂肪酶、碱性脂肪酶的酶解后酶活力,饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸组成,分析腌腊肉制品贮存过程中游离脂肪酸的变化及其影响因素,进而考察游离脂肪酸的来源途径。结果表明:相同条件下,全瘦肠、肥瘦质量比3∶7腊肠、肥瘦质量比4∶6腊肠游离脂肪酸的含量依次降低;不同产地游离脂肪酸含量差异显著;贮存温度37℃时游离脂肪酸的含量明显高于25℃;灭酶腌腊制品比不灭酶产品的游离脂肪酸增幅较小,且差异逐渐增大。脂肪水解酶在腌腊肉制品游离脂肪酸产生过程中发挥了重要的作用,贮存前期,酶促反应的持续进行,游离脂肪酸不断产生,脂肪水解是主导作用,而贮存后期不饱和脂肪酸不稳定逐渐被氧化,脂肪氧化起到关键作用。     

Changes in flour lipids during the storage of wheat flour

High- and low-grade spring and winter wheat flours of ～13% moisture were stored at 15, 25 and 37 °C and the lipids were then extracted with water-saturated n-butanol. In the original (control) flours there were more neutral lipids and glycolipids in low-grade winter than in high-grade winter and in low-grade spring than in high-grade spring flours, but there were no corresponding differences in the amounts of phospholipids. The total extractable lipid contents of the flours remained constant in the samples stored at 15 °C, but there were slight losses in the samples stored at 25 and 37 °C. Total lipid contents determined by acid hydrolysis remained constant in all cases indicating that no loss of fatty acids had occurred on storage. There was sufficient hydrolysis of all glycerides to account for the increased amounts of free fatty acids in the stored flours. Some complete deacylation of lipids to free fatty acids and water-soluble products was indicated. The fatty acid composition of all lipids remained constant, and there was no evidence of any lipoxygenase or other enzymic degradation of fatty acids. Stereoanalysis of the principal glycerides indicated that phosphatidylcholine (and probably also phosphatidylethanolamine) was specifically hydrolysed at the 2-position, presumably by phospholipase-A₂. Hydrolysis of triglycerides, diglycerides and monoglycerides was attributed to the action of wheat and microbial lipases of unknown specificity. Stereoanalysis of N-acylphosphatidylethanolamine and the galactosyldiglycerides was not attempted, but it was deduced that they were randomly hydrolysed at the 1- and 2-positions. The changes found in the flour lipids differed from those reported to occur in germinating wheat and in stored damp wheat flour which had been damaged by moulds.     

Evaluations of Warmed-over Flavor during Chill Storage of Cooked Broiler Breast, Thigh and Skin by Chemical, Instrumental and Sensory Methods

Broiler breast, thigh and skin were cooked to 80°C, stored at 2°C for up to 5 days, and evaluated by chemical, gas chromatographic (GC) and sensory methods. Water and fat content of cooked meat did not change during storage. Thiobarbituric acid (TBA) values and levels of major headspace volatiles increased throughout storage time. Intensities of cardboard, warmed-over, rancid/painty, and overall off-flavor characteristics increased. Skin showed the least changes. Breast and thigh meat differed in GC profiles but were similar in sensory scores after 1 day and in TBA values after 2 days of storage. Both TBA and headspace GC measurements are associated with the off-flavor development.     

Effects of marination, cooking and storage on physico-chemical and microbiological properties of ready to eat trout döner kebab

The aim of this work was to investigate the use of rainbow trout (Oncorhynchus mykiss) in ready to eat döner kebab production and determine the effects of marination, cooking and storage conditions (4 and ?18 °C) on physico-chemical and microbiological properties of döner kebab. The raw trout meat, raw, cooked and stored döner kebab samples were subjected to moisture, protein, fat, ash, color, pH, cholesterol, biogenic amines, lipid oxidation, fatty acids profile, texture, microbiological and sensory analysis. The results indicated that the major fatty acids in trout döner kebab were palmitic, stearic, oleic, omega-3 and omega-6 fatty acids and unsaturated fatty acids were higher than saturated fatty acids (p < 0.05). Low biogenic amine and cholesterol contents were determined in döner kebab. It was found that ?18 °C of storage temperature was more effective than 4 °C for inhibition of lipid oxidation and microbial growth in trout döner kebab (p < 0.05). While cooking affected parameters evaluated (p < 0.05), marination did not have any significant effect. The study results indicated that using rainbow trout meat in döner kebab production could be beneficial to provide healthy meat products without posing any acceptability problems in terms of quality factors. This is the first paper to be reported on physico-chemical and microbiological properties of döner kebab produced with rainbow trout and effects of marination, cooking and different storage temperatures on these physico-chemical and microbiological properties.