Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged.     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged. Received: 16 March 1998 / Revised version: 17 June 1998     

Effect of the packaging method and the storage time on lipid oxidation and colour stability on dry fermented sausage salchichón manufactured with raw material with a high level of mono and polyunsaturated fatty acids

The effects of fatty acid composition, two packaging methods (vacuum and 20% CO₂/80% N₂) and storage under refrigeration for 210 days were evaluated on a dry fermented sausage (salchichón), manufactured with raw material enriched in monounsaturated or polyunsaturated fatty acids. Fatty acid composition was determined on sausage mixtures and on ripened sausages and lipid oxidation and colour stability was determined on ripened sausage at different times during storage. The modification of fatty acid composition of the sausages raised the nutritional quality, slightly affecting the colour properties. Dry fermented sausages enriched in polyunsaturated and monounsaturated fatty acids presented higher lipid oxidation values than the control ones. Both packaging methods (vacuum and 20% CO₂/80% N₂) during 210 days of chilled storage had minor effects on the colour and the lipid oxidation stability.     

Relation between types of packaging,frozen storage and grilling on cholesterol and fatty acids oxidation in Atlantic hake fillets (Merluccius hubbsi)

Two different commercial samples of frozen and packaged, in low and high-oxygen permeability packaging, Atlantic hake fillets were stored at −18 °C for 4 months and the intensity of lipid oxidation, as well as the formation of cholesterol oxidation products (COP), during storage and subsequent grilling were studied. Raw fillets at the initial time of storage showed low total COP levels, however, after 120 days of storage the concentrations were raised significantly, under both packed conditions. During freezing and subsequent grilling there was a significant decrease (p < 0.02) in the contents of the cholesterol and polyunsaturated fatty acids in all the hake samples. Correlations were found between the cholesterol and fatty acid parameters and cholesterol oxides formation during storage and heat treatment. The commercial frozen storage with a low-oxygen permeability packaging was more effective in preventing lipid oxidation than high-oxygen permeability packaging, with less accented cholesterol degradation as well as cholesterol oxides formation.     

Cellulose nanoparticles synthesised from potato peel for the development of active packaging film for enhancement of shelf life of raw prawns (Penaeus monodon) during frozen storage

In this study, the cellulose nanoparticles (CNP) isolated from potato peel were used for reinforcement of polyvinyl alcohol (PVA)-based active packaging film. The above film was used to pack the raw prawns (Penaeus monodon) at −20 °C, and the colour change, protein content, TVB-N, TMA and microbial analysis were done at regular interval for prawns stored in CNP-PVA active packaging film. A significant difference was observed in the quality of prawns stored in potato CNP-PVA film compared with prawns packed and stored in polyethylene film. The newly designed active packaging with CNP and fennel seed oil enhanced the shelf life of prawns up to two months for both HOSO (head on shell on) prawn and PD (peeled and deveined) prawn. Hence, the study recommends the potato peel CNP-PVA film with fennel seed oil as better choice to extend the shelf life of the prawns during storage compared with polyethylene packaging.     

气调包装结合电子束辐照对蚌肉冰藏品质的影响

为进一步分析气调包装结合电子束辐照对冰藏蚌肉品质的影响,该研究设置对照组（CK）、气调包装组（Modified Atmosphere Packaging,MAP）、电子束辐照组（Electron Beam Irradiation,EB）以及气调包装结合电子束辐照组（Modified Atmosphere Packaging Combined with Electron Beam Irradiation,MAP+EB）,通过测定冰藏初始点和货架期终点时蚌肉的质构、色泽、挥发性风味物质和脂肪酸组成指标综合评价蚌肉的品质。结果表明,电子束辐照后蚌肉的硬度、咀嚼性降低,但可延缓微生物繁殖对蚌肉质构的影响。蚌肉色差值在冰藏初始点各组间无显著差异（P>0.05）,在货架期终点,受电子束辐照影响,EB组和MAP+EB组的L*值下降,b*值上升。冰藏初始点,CK、MAP、EB和MAP+EB组蚌肉中挥发性风味物质的种类分别为8、17、16和19种,说明气调包装和电子束辐照处理显著提高挥发性风味物质的种类（P<0.05）,并且醛类、酮类物质总含量提高,烃类、醇类物质总含量降低,但无显著差异（P>0.05）。各保鲜组蚌肉中脂肪酸相对总含量分别为49.55%、49.64%、49.61%和49.90%,无显著差异（P>0.05）。综上,气调包装结合电子束辐照对冰藏蚌肉的贮藏品质无明显的不良影响,适合于蚌肉的物理保鲜。     

Protection of Menhaden Mince Lipids from Rancidity during Frozen Storage

Several antioxidants as well as vacuum packaging and changes in frozen storage temperatures (-7°C and -20°C) were tested for their effect on the peroxide values and free fatty acids (FFA) of frozen minces from Gulf menhaden, Brevoortia patronus and Atlantic men-haden, Brevoortia tyrannus. Vacuum packaging was the most effective in retarding oxidative rancidity. Storage at -20°C also reduced the oxidation versus -7°C. Ascorbic acid and crythorbic acid had the best antioxidant activity of the additives tested. Tocopherols, rosemary extracts, and tertiary butylhydroquinone (TBHQ) had limited antioxidant activity. Storage at -20°C inhibited hydrolytic rancidity. Neither vaccum packaging nor any of the additives prevented FFA development at -7°C.     

不同包装方式下冷鲜青虾的菌群多样性分析

对青虾采用两种包装方式：托盘包装和气调包装（体积分数50% CO2＋50% N2）,在4?℃条件下贮藏6?d,测定菌落总数和挥发性盐基氮含量,确定不同包装方式下青虾的货架期;随后利用16S?rDNA扩增子测序对两种包装方式下青虾微生物多样性进行研究,比较其菌相变化,确定其变化规律。结果表明：托盘包装组和气调包装组的货架期分别为2?d和4?d;且两种包装方式下变质青虾的菌群结构有较大差异,在托盘包装方式下,优势菌群主要以不动杆菌、黄杆菌和希瓦氏菌为主,是普通低温贮藏时造成青虾腐败的主要菌群;采用气调包装后,黄杆菌和希瓦氏菌数量大大降低,假单胞菌成为主要优势菌群;体积分数50%?CO2＋50%?N2气调包装能抑制托盘包装时优势腐败菌的增殖,从而延长货架期;而假单胞菌有较强的耐受力,成为新的优势腐败菌。研究结果为保障青虾的质量安全提供了理论依据。     

Changes in fatty acids of frog legs during frozen storage

The changes in the fatty acids of frog leg meat during frozen storage were studied with column and gas-liquid chromatography. The major component of the lipids, the phospholipids constituted 90% of total lipids. 16:0, 18:0, 22:0 and 18:2 polyunsaturated fatty acid were the major fatty acids of the frog legs meat lipids. Short chain fatty acids were noticed to the extent of 10%. During frozen storage the proportion of phospholipids decreased, while that of neutral lipids increased. Since the total lipid content was constant, phospholipases were presumably responsible for this change. Alterations in the fatty acid composition of the neutral lipids during storage were consistent with such a hypothesis.     

Changes in the quality of fishburger produced from Tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) during frozen storage (−18 °C)

In this study, the chemical and sensory qualities of fishburger produced from tilapia (Oreochromis niloticus) were investigated during frozen storage (–18 °C) over 8 months. The ratios of crude protein, lipid, moisture, crude ash, and polyunsaturated fatty acids in tilapiaburger were found to be 17.82%, 5.29%, 66.68%, 2.56% and 7.95% respectively. At the end of the study, the total volatile basic nitrogen value was found to have fluctuated throughout the storage periods. The highest thiobarbituric acid value was found at the 7th month as 0.142 mg malonaldehyde/kg. The peroxide value was 0.18 meq/kg at the beginning of the storage but increased to 5.03 meq/kg at 6th month of storage and then decreased to 0.82 meq/kg at the 8th month. The level of free fatty acids was 2.73% oleic acid at the beginning but reached 4.14% in the first month of storage and then increased to 5.92% at the end of the storage. pH values ranged between 8.01 and 7.97. At the end of the storage period, sensory quality criteria were scored as quite near those of the fresh samples.     

Differences in chemical, microbial and sensory quality parameters of the marinated ascidia Microcosmus sabatieri Roule, 1885 during storage at 6 °C under vacuum conditions

Chemical, microbial and sensory quality aspects of the marinated ascidia Microcosmus sabatieri Roule, 1885, were examined over a 150-day period at 6 °C, under vacuum and air (control) packaging conditions using three different formulations (with 12% sodium chloride and 3%, 5% or 7% acetic acid). Significant differences were found between chemical and sensory analysis of three different marinated groups ( P  > 0.05) during the storage period. There were also significant differences in pseudomonads, lactic acid bacteria and yeast and moulds of the marinated groups by which lower bacterial counts were determined. N -3 polyunsaturated fatty acids concentrations decreased significantly ( P  < 0.05), while total viable counts, ammonia and total saturated fatty acid concentrations increased significantly ( P  > 0.05) in all three groups during storage. The differences in fatty acid and ammonia concentrations were found to be useful as indexes of freshness and decomposition of marinated M. sabatieri in storage. Shelf life of M. sabatieri marinades was found to be 5 and 4 months under vacuum and air (control) packaging conditions respectively, at 6 °C.     

Culinary herbs inhibit lipid oxidation in raw and cooked minced meat patties during storage

The effect of dried spices and the ethanol extract of those spices was studied on the stability of fresh chicken minced meat, and fresh and cooked pork patties pretreated with NaCl during refrigerated and frozen storage. The antioxidant activities of the spices were measured by thiobarbituric acid reactive substances (TBARS) and peroxide value (POV) in meat samples. The lipid oxidation was effectively inhibited in the chicken meat treated with several dry spices diminishing the TBARS to a range of 32% and 83% of those found in the control samples in frozen stored meat for 6 months. Marjoram, wild marjoram and caraway were the most effective dry spices. Ethanolic extracts of the same spices were more potent as antioxidants by lowering the concentration of the TBARS to a range of 20–27% of those found in the control samples. Addition of sodium salt to the minced pork resulted very high concentrations of the oxidation products originated from the polyunsaturated fatty acids. The treatment with ethanolic extract of spices (sage, basil, thyme and ginger) significantly inhibited the lipid peroxidation in refrigerated and chilled pork patties pretreated with NaCl by reducing both POV and TBARS. Heat treatment with microwaves produced significantly elevated levels of both lipid peroxides and TBARS, but the amount of these oxidation products was less than 10% in spice‐treated salted meat samples compared to that in untreated ones. Lipid peroxidation also grew continuously during the storage period at −18°C in raw and cooked samples. Ethanolic extracts of spices had a very strong antioxidative effect inhibiting lipid peroxidation in heat‐treated meat products during frozen storage. The highest antioxidant activity was observed in the case of ginger. High correlation coefficients were found between TBARS and POV both in raw and cooked pork patties (0.86, 0.91, respectively) during frozen storage. It is supposed that these compounds originated from the polyunsaturated fatty acids during oxidation processes but at different stages. Utilization of spices, spice mixtures or spice extracts in semi‐prepared meat products intended to be frozen for up to 6 months or more before consumption is proved to be advantageous in regard of shelf life of the food, as well as of human health, because of the beneficial effect of spices in inhibition of lipid peroxidation during heat treatment and chilling storage. © 1999 Society of Chemical Industry     

Characteristics of pork products from swine fed a high monounsaturated fat diet: Part 3-A high-fat cured product

Fresh pork bellies from animals fed a control sorghum-soybean diet and a similar diet containing 12% high-oleic sunflower oil (HOSO) were cured and processed in a smokehouse to an internal temperature of 55·6°C. Cooking losses were not significantly different (p < 0·05) between bacon strips from animals on the control diet and those from animals on the HOSO diet. The ratio of monounsaturated fatty acids to saturated fatty acids for the cooked rasher from the HOSO group was 1·84 times that for the cooked rasher from the control group (2·48 versus 1·35). The cooked rasher had a slightly lower (p < 0·05) percentage of total monosaturates that uncooked bacon strips within each diet group. When considering stearic acid as a fatty acid that does not raise the plasma cholesterol level in the human, along with all unsaturated fatty acids, only 16·83% and 12·26% of total fatty acids in the cooked rasher and the drip, respectively, from the HOSO group were fatty acids (C14:0 and C16:0) which may raise the plasma cholesterol level. The residual nitrite level in the raw and cooked bacon was higher (P < 0·05) for samples from the HOSO group than for those from the control group, probably due to binding of nitrite to the double bonds in unsaturated fatty acids that were higher for samples from the HOSO group. The extent of the accumulation of thiobarbituric acid-reactive substances during frozen storage was not affected (P > 0·05) by the inclusion of 12% HOSO in the animal diet, regardless of the packaging method.     

Effects of cooking and reheating methods on the fatty acid profile of sea bream treated with rosemary extract

BACKGROUND: The effects of rosemary extract on the fatty acid profile of sea bream fillets cooked by different methods (oven baking, grilling and pan frying) as well as the effects of different reheating methods (microwave and conventional oven) on the fatty acid composition of fish after frozen storage for 4 months were investigated. RESULTS: The proportion of saturated fatty acids increased only slightly in fried samples but significantly in oven‐baked and grilled samples, while the proportion of polyunsaturated fatty acids (PUFAs) increased significantly in fried samples but only slightly in oven‐baked and grilled samples. The proportion of monounsaturated fatty acids remained relatively constant after cooking. Of the fatty acids analysed, the most significant increases (P < 0.05) were observed in C18:1n‐9 and C18:2n‐6 and the most significant decreases (P < 0.05) in C14:0, C16:1, C20:5n‐3 and C22:6n‐3. Although sea bream fillets fried in sunflower oil showed an increase in PUFAs, the lowest eicosapentaenoic and docosahexaenoic acid contents were found in fried samples. CONCLUSION: Sea bream fillets treated with rosemary extract showed slower oxidation than untreated fish. Neither conventional nor microwave reheating after frozen storage for 4 months had a detrimental effect on the fatty acid profile and its stability. Copyright © 2009 Society of Chemical Industry     

Antioxidants from barley husks impregnated in films of low-density polyethylene and their effect over lipid deterioration of frozen cod (Gadus morhua)

BACKGROUND: The changes in quality of cod fillets packaged in films with and without antioxidants during 12 months of frozen storage at ? 20 °C were investigated in the present study. The following parameters were determined in order to study lipid hydrolysis and primary and secondary lipid oxidation in the samples during frozen storage: peroxide value, conjugated dienes, conjugated triene hydroperoxides, free fatty acids, totox value, thiobarbituric acid‐reactive substances and p‐anisidine value. RESULTS: Films containing antioxidants isolated from barley husks were effective in slowing down lipid hydrolysis and primary and secondary lipid oxidation processes. Secondary lipid oxidation reached maximum values in the 12th month of storage in control samples and samples packaged with antioxidant‐containing film. Maximum lipid hydrolysis and lipid oxidation values for control cod samples were significantly higher than the maximum values found in samples packaged with antioxidant‐containing film. CONCLUSION: The results confirm the efficacy of natural antioxidants derived from barley husks in slowing down lipid hydrolysis and increasing the oxidative stability of cod flesh. They also demonstrate the potential usefulness of natural antioxidants extracted from barley husks in the development of active packaging films for food preservation. Copyright © 2011 Society of Chemical Industry     

The impact of dietary oil source and frozen storage on the physical,chemical and sensorial quality of fillets from market-size red hybrid tilapia, Oreochromis sp.

Red hybrid tilapia (Oreochromis sp.) were fed one of four diets containing either fish oil, crude palm oil, palm fatty acid distillates or refined palm olein as the only added oil. Post-harvest fillet quality was then evaluated at 1, 10 and 30 weeks of frozen storage. Dietary oil source did not significantly (p > 0.05) influence the liquid holding capacity and texture of fillets but both these parameters were increased by frozen storage. Fillets from fish fed palm oil-based diets exhibited significantly higher oxidative stability during frozen storage, compared to fish fed the fish oil diet. Dietary oil source and frozen storage had little impact on sensory attributes. Unlike fillet proximate composition, fillet fatty acid composition was significantly affected by both diet and frozen storage. Total n-3 polyunsaturated fatty acids decreased significantly in the fillet lipids of all fish after 30 weeks of frozen storage.     

Free Fatty Acids from Orange Juice Absorption into Laminated Cartons and their Effects on Adhesion

Orange juice was stored in polyethylene/aluminum foil laminated cartons at 8°C room temperature (RT), 35°C, and 55°C for up to 1 yr. Studies were carried out on the formation of 6 major free fatty acids (FFAs) in orange juice and their absorption into packaging materials during storage. Simultaneously adhesion tests on packaging materials were performed. Depending on storage temperature FFA concentrations increased steadily during storage and they were absorbed (in parallel) into the food contact layer of the packaging materials. Delamination between the plastic layer and aluminum foil occurred when a critical absorption level of 4–5 mg/dm² packaging material (corresponding to a level of 10.5–13.2 mg/cm³ or 1.1–1.4% in the inside polymer layer) was exceeded.     

鲐鱼低温冻藏过程中脂肪氧化特性

鲐鱼组氨酸含量较高,在低温贮藏中品质易发生劣变,影响其食用安全性。以－18 ℃冻藏的鲐鱼为研究对象,在贮藏0、10、20、40、60、80、100 d后分别取样,测定鲐鱼风味、过氧化值、酸价、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARs）值和脂肪酸成分的变化,研究低温冻藏过程中鲐鱼脂肪氧化规律。结果表明：冻藏初期,鲐鱼中风味物质以氮氧化合物为主,随着冻藏时间的逐渐延长,各挥发性风味物质响应强度逐渐增强;鲐鱼的酸价和过氧化值呈现先上升后下降再上升的趋势;鲐鱼的TBARs值呈现明显的上升趋势,且贮藏时间越长,增加速率越快;鲐鱼的饱和脂肪酸含量随着冻藏时间的延长而增加,而不饱和脂肪酸含量呈下降趋势,脂肪氧化程度增强。     

冻结及冻藏温度对小龙虾冻藏过程中脂质氧化的影响

本研究将小龙虾热烫后置于真空包装盒内,灌水并抽真空,分别于3 种冻结温度（－20、－40 ℃和－55 ℃）的冰柜内冻结至中心温度为－15 ℃,再于2 种冻藏温度（－20 ℃和－40 ℃）的冰柜中冻藏24 周,测定不同温度冻结和冻藏小龙虾肉的脂肪质量分数、游离脂肪酸（free fatty acids,FFAs）含量以及脂肪酸组成、过氧化值（peroxide value,POV）和硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARS）值,探讨冻结及冻藏温度对小龙虾脂质氧化的影响。结果表明：随着冻藏时间的延长,6 组小龙虾的脂肪质量分数、不饱和脂肪酸（unsaturated fatty acids,UFAs）和多不饱和脂肪酸（polyunsaturated fatty acids,PUFAs）相对含量显著下降（P＜0.05）,FFAs含量和饱和脂肪酸（saturated fatty acids,SFAs）相对含量、POV、TBARS值总体显著上升（P＜0.05）。冻藏温度相同时,－20 ℃冻结的小龙虾肉的POV、TBARS值高于－40 ℃和－55 ℃,而FFAs含量和脂肪酸组成无明显差异;冻结温度相同时,－20 ℃冻藏小龙虾肉脂肪和FFAs含量、POV、TBARS值均明显高于－40 ℃冻藏组,UFAs和PUFAs含量低于－40 ℃冻藏组,SFAs含量高于－40 ℃冻藏组。结论：冻结温度－40、－55 ℃和冻藏温度－40 ℃均减轻了小龙虾肉脂质的水解和氧化程度。     

Non-Volatile Organic Acids,pH and Titratable Acidity Changes in Pineapple Fruit Slices During Frozen Storage

Effects of freezing and frozen storage on pH, titratable acidity and non-volatile organic acids of two pineapple fruit cultivars, Smooth Cayenne and Red Spanish, were studied. Pineapple fruit was frozen as slices in a cold room at −18°C and stored at this temperature for a 12 month period. A negative correlation was found between pH and titratable acidity in the two cultivars throughout frozen storage ( r =-0·67 for Smooth Cayenne and r =-0·71 for Red Spanish). Non-volatile organic acids were determined by high performance liquid chromatography. The major components were citric and L-malic acids. A high correlation was found between these two acids during frozen storage ( r =0·75 in Smooth Cayenne and r =0·78 in Red Spanish). There were significant differences ( P⩽ 0·01) in pH and titratable acidity between the two studied varieties after a year of frozen storage. Significant differences ( P⩽ 0·05) were found in pH values during frozen storage in cv Smooth Cayenne and in citric and L-malic acids in cv Red Spanish. Freezing preservation of pineapple fruit slices led to minimal chemical changes after a year of frozen storage.