Changes in the fatty acid composition of dietetic ready-to-cook chicken meat products during frozen storage

A study was made on the fatty acid composition of dietetic ready-to-cook products of boneless chicken legs or breasts prepared by curing using several curing mixtures during frozen storage. Leg muscles were found to be richer in unsaturated fatty acids than breast muscles, substantial differences having been found in the contents of palmitoleic and linolenic acids. During frozen storage, the contents of unsaturated fatty acids were reduced, especially intensively in the leg muscle ready-to-cook products. The fastest changes occurred in linolenic and linolic acids and partly in palmitic acid. The level of oleic acid remained substantially unchanged throughout the storage period. Irrespective of the changes found, the ratio of unsaturated and saturated fatty acids in all the groups studied remained greater than 1 for both types of meat. The application of citrate in the curing mixture had a favourable effect on the changes, in that a minimum alteration in the contents of unsaturated fatty acids was achieved.     

Changes in free fatty acid composition during storage of whole milk powder

Changes in fat matter due to the microbial thermostable lipases are among the most significant deteriorations influencing the shelf life of whole milk powder. As a consequence, free fatty acids are produced, being the short-chain acids mainly responsible for the rancidity flavour. The aim of this work was to evaluate changes in different fatty acid concentrations during the storage of whole milk powder produced in two different seasons. Samples of whole milk powder produced in winter and summer and packed under inert atmosphere were used in the study. The samples were stored at 21°C and 40°C. Samples stored at 21°C were evaluated every 3 months, whereas samples stored at 40°C were evaluated monthly by free fatty acids profile and sensory analysis. Data were processed by principal component analysis and anova . Results showed that changes in the free fatty acids of milk powders were correlated with the season of manufacture. Temperature and storage time had little influence on that profile.     

紫花苜蓿籽油的理化性质及必需脂肪酸组分分析

研究了采用2种有机溶剂法提取的紫花苜蓿籽油的理化性质和必需脂肪酸组成。结果表明:无水乙醚、丙酮浸提的苜蓿籽油的折光指数分别为1.4780±0.025、1.4795±0.031;碘值分别为(135.60±0.132)、(130.12±0.156)g/100g;酸价分别为(3.30±0.056)、(3.12±0.043)mg/g;皂化值分别为(188.40±0.421)、(175.47±0.356)mg KOH/g;过氧化值分别为(0.299±0.012)、(0.599±0.026)mmol/kg,这些指标与常见植物油的理化性质基本相符。气相色谱法分析结果显示,丙酮浸提的紫花苜蓿籽油中必需脂肪酸含量较高,其中亚油酸含量为1 2.1 4%,α-亚麻酸含量为2 6.7 9%,适合作为食用油开发。     

烟台大樱桃仁油理化性质及脂肪酸组成分析

初步分析烟台大樱桃仁油的理化性质及脂肪酸组成,旨在为开发新型功能性油脂——烟台大樱桃仁油以及樱桃仁的综合利用提供理论依据。采用气相色谱对烟台大樱桃仁油的脂肪酸组成进行了分析,并对该油脂的理化性质进行了研究。结果表明:从该油脂中分离出10种脂肪酸,主要为亚油酸(39.14%),油酸(36.09%),棕榈酸(7.79%),硬脂酸(2.96%),花生酸(1.49%),不饱和脂肪酸质量分数达76.2%,属于高油酸-亚油酸型油脂;烟台大樱桃仁油含油率为27.8%,其主要理化指标为:酸价1.87 mg KOH/g,过氧化值8.95 mmol/kg,碘值118 g I/100 g,皂化值184 mg KOH/g,不皂化物1.67%。烟台大樱桃仁油作为油料新品种进行开发,必将产生很高的经济效益和社会效益。     

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.     

冻藏对小麦淀粉理化性质及热力学特性的影响

研究了冻藏对小麦淀粉颗粒表面形态、理化性质、热力学性质及凝沉特性的影响。通过扫描电镜(SEM)检测冻藏小麦淀粉颗粒,发现部分淀粉颗粒表面有破损;对冻藏后的小麦淀粉溶解度、粘度、膨润力、蓝值等进行测定,结果显示冻藏后淀粉溶解度和粘度分别增大了48.6%、43.2%;膨润力、蓝值分别降低8.41%、28.5%;采用示差量热扫描(DSC)测定冻藏小麦淀粉热力学性质变化,发现冻藏小麦淀粉糊化热焓降低了47.3%,糊化温度起止范围降低了10.60%;凝沉值降低了47.2%。研究表明冻藏后的小麦淀粉颗粒形态,理化性质、热力学性质均发生了明显改变。      

超声处理对红花籽油理化性质及脂肪酸组成的影响

研究了不同超声条件下,红花籽油过氧化值、酸值、皂化值及脂肪酸组成的变化规律。结果表明:超声温度控制在50℃以下,超声功率小于等于600 W,超声时间短于60 min时,超声处理对红花籽油的过氧化值、酸值无明显影响,当超声功率高于600 W时,过氧化值、酸值随超声时间的延长而增加;超声温度控制在50℃以下,超声功率小于等于900 W,超声时间短于60 min时,超声处理对红花籽油脂肪酸组成没有影响,对脂肪酸含量和皂化值有较小的影响。     

不同冷冻方式下猪肉贮藏期持水力的变化

采用浸渍冷冻(-35℃)与风冷冷冻(-35℃)两种方法,将猪背长肌中心温度从10℃分别降到-5℃与-18℃,再置于相应温度的冰箱里保藏.在1个月贮藏期间,测定解冻汁液流失率、蒸煮损失率与加压失水率,同时利用低场核磁共振技术(LF-NMR)测定弛豫性质变化(T2),来反映贮藏期间猪肉持水力的变化,并探讨T2值与解冻汁液流失率、蒸煮损失率与加压失水率之间的相关性.结果表明:浸渍式冷冻肉块的各项指标均优于风冷式冷冻,在贮藏14 d之前,浸渍-5℃肉块的T21值(30～60 ms)、T22值(100～400 ms或200～500 ms)、解冻汁液流失率、蒸煮损失率与加压失水率都显著低于浸渍-18℃组,但贮藏14 d后反之.通过核磁共振技术测定出的T21值、T22值与蒸煮损失率、解冻汁液流失、加压失水率具有相同的变化趋势.     

传统作坊式压榨菜籽油理化指标和脂肪酸分析

选取2种传统压榨菜籽油,与市售的四级压榨菜籽油,按照国家4级油标准,在酸值、过氧化值、生育酚、甾醇、脂肪酸含量等方面进行了比较分析。研究表明:传统作坊压榨菜籽油在色泽、理化指标和脂肪酸组成中符合国家4级油标准,在油酸、亚油酸、生育酚等方面含量远远高于国家标准和市售商品油。     

Resistance to freezing and frozen storage of Streptococcus thermophilus is related to membrane fatty acid composition.

The resistance to freezing and frozen storage of Streptococcus thermophilus was related to the fatty acid composition of the cell membrane. The effects of four experimental factors were investigated on the fatty acid concentrations and on the recovery of acidification activity of S. thermophilus stored at -20 degrees C by using a complete experimental design: incorporating oleic acid in the culture medium, fermentation pH, addition of glycerol as cryoprotective agent and duration of storage. The acidification activity decreased during the freezing and the frozen storage of S. thermophilus. The storage time slightly enhanced the unsaturated fatty acid concentrations. The addition of glycerol did not modify the fatty acid composition but increased the resistance to frozen storage. The addition of oleic acid and the decrease of the fermentation pH enhanced the ratio unsaturated:saturated fatty acids and improved the recovery of the acidification activity. These results indicate that the resistance to frozen storage was closely related to the membrane fatty acid composition. We interpreted this as an adaptation of S. thermophilus to the addition of oleic acid and the unfavorable growth conditions that corresponded to a low fermentation pH.     

Changes in physicochemical properties of pork myofibrillar protein combined with corn starch and application to low-fat pork patties

The aim of this study was to evaluate the physicochemical properties of pork myofibrillar protein (MP) gels as affected by different additional levels of corn starch and microbial transglutaminase (MTGase) and applied to pork patties at two levels of corn starch. MPs with MTGase have higher properties than those without MTGase, except cooking loss (CL), which improved with higher corn starch concentrations. Although gel strength did not differ among the treatments, microstructures of corn starch were swollen, which proved that they were holding water. When corn starch was added, CL and thawing loss decreased, but shear value increased. The diameter shrinkage values of pork patties decreased with increasing corn starch concentrations. In addition, the pork patties with 2 g/100 g corn starch have a higher water-holding capacity than the controls. The meat industry could use 1.0 g/100 g corn starch as a water-binding agent to manufacture pork patties.     

Changes in lipid composition and fatty acid profile of Nham,a Thai fermented pork sausage,during fermentation

Changes in lipid composition and fatty acid profile of Nham during fermentation were investigated. Total lipids of Nham were in the range 2–3%. The extracted lipid of initial Nham mix consisted mainly of triglycerides (TG), accounting for more than 75% of the total lipid, followed by phospholipids (PL) and a trace amount of diglycerides (DG) and free fatty acid (FFA). During fermentation, TG, DG and PL decreased with a concomitant increase in FFA, indicating lipolysis of Nham lipids during fermentation. Changes in fatty acids of the total lipids, non-polar and polar lipid fractions were observed during fermentation. In both total and non-polar lipid fractions, the major fatty acids found in a descending order were oleic (C18:1), linoleic (C18:2) and palmitic (C16:0) acids, which together accounted for 90% of the total fatty acids. Increases in fatty acid contents in both total and non-polar lipid fractions, were observed with a corresponding decrease in the quantity of fatty acids of phospholipids. As the fermentation proceeded, peroxide value generally increased while TBARS values decreased. Overall, lipid oxidation in Nham occurred during fermentation but did not cause the objectionable odour and taste in any Nham tested.     

蓖麻油的理化性质及脂肪酸组成分析

对一级蓖麻油的理化性质进行了测定,并利用气相色谱-质谱联用仪（GC—MS）对蓖麻油的脂肪酸组成进行了分析和鉴定。     

密封条件下冰温贮藏猪里脊肉的质构及理化特性变化

选取宰后4 h的新鲜猪里脊肉,以全质构(texture profile analysis, TPA)、挥发性盐基氮(total volatile base nitrogen,TVB-N)、色泽、pH值为参考指标,分别在第0、2、4、6、8、10、12、14、16、18天进行指标测定,综合评定冰温贮藏18 d内猪里脊肉品质变化。结果表明:随着贮藏时间的延长,猪里脊肉的硬度值下降(P0.01),咀嚼性逐渐降低(P0.05),弹性、内聚性和回复性变化不明显(P0.05),贮藏第6～8天,肉样TPA变化规律开始明显改变;TVB-N在贮藏期间逐渐升高(P0.01),在第16天达到二级鲜肉标准为15.62 mg/100 g;L~*值、a~*值、b~*值呈现出先升高后降低的变化趋势(P0.05),并在贮藏第12天出现最大值。因此,密封条件下冰温贮藏猪里脊肉色泽良好、肉质新鲜,可在不破坏细胞结构的基础上有效地延长了猪肉的贮藏期。     

鼠尾草酸对椰子油热加工过程中主要理化性质、脂肪酸组成与自由基的影响研究

以叔丁基对苯二酚(TBHQ)为对照,对比分析鼠尾草酸(CA)对椰子油热加工过程(180℃)中主要理化指标(酸价、游离脂肪酸含量、过氧化值、总氧化值、茴香胺值)、脂肪酸组成及自由基含量的影响。结果表明:加入抗氧化剂能够显著降低椰子油的主要理化指标, CA与TBHQ效果基本相当;加入CA和TBHQ可以抑制和延缓反式油酸、反式亚油酸的产生;CA和TBHQ对椰子油热加工过程中自由基含量的增加具有明显的抑制作用,且CA的抑制效果与TBHQ相差不大。因此,可以考虑将CA作为TBHQ在油脂热加工过程中的替代抗氧化剂使用。     

Effect of crossbreeding and gender on meat quality and fatty acid composition in pork

This study considers the effect of crossbreeding and gender (barrows; gilts) on meat quality and intramuscular and subcutaneous fatty acid composition in pork. The sire lines included Large White (LW), Duroc (D) and Pietrain (P) and the dam line was Landrace (LR)×LW, producing LW×(LR×LW), D×(LR×LW) and P×(LR×LW). Pork samples were removed from Longissimus dorsi (LD) and Semimembranosus (SM) muscles and subcutaneous fat (SCF). There were no important differences in meat quality parameters but D×(LR×LW) had the highest percentage of intramuscular fat. Castrated males had more intramuscular fat and more intense meat colour than female pigs. The Large White and Duroc sire line had saturated fatty acids (SFA) in SM, whereas the Pietrain sire line was significantly higher than Duroc sire line in the concentration of polyunsaturated fatty acids (PUFA), PUFA/SFA (P/S) and the n-6/n-3 ratio. The concentrations of SFA and monounsaturated fatty acids (MUFA) in SCF were significantly higher in LW×(LR×LW) and P×(LR×LW), respectively. No differences were found in the percentage of PUFA, P/S and n-6/n-3 ratio between D×(LR×LW) and P×(LR×LW). Female pigs had the most polyunsaturated intramuscular and subcutaneous fat. The results demonstrate small differences in fatty acid compositions among sires.     

The effect of replacing fat with oat bran on fatty acid composition and physicochemical properties of meatballs

Oat bran was used as a fat substitute in the production of meatballs. The effect of oat bran addition on the fatty acid composition, trans fatty acids, total fat, some physicochemical and sensory properties of the samples was studied. Meatballs were produced with four different formulations; the addition of 5, 10, 15 and 20% oat bran. Control samples were formulated with 25% fat addition as in commercial production. The major fatty acids were cis-oleic, palmitic and stearic acid in all the meatball samples, those with oat bran added as well as the control. Meatballs containing oat bran had lower concentrations of total fat and total trans fatty acids than the control samples. Meatballs made with 20% oat bran had the highest protein, salt and ash contents, L value (lightness), b value (yellowness), and the lowest moisture content and a value (redness). There was no significant difference among the meatball samples with respect to sensory properties, and all samples had high acceptability.     

Irradiation effect on fatty acid composition and conjugated linoleic acid isomers in frozen lamb meat

The effect of gamma radiation processing on the lipid content, fatty acid composition and conjugated linoleic acid (CLA) profile in frozen lamb meat was investigated. Samples of longissimus thoracis muscle from lambs fed lucerne basal diets either unsupplemented or supplemented with polyunsaturated vegetable oils were irradiated (7 kGy) and analysed. CLA contents in lamb meat did not affect (P > 0.05) the levels of lipid oxidation induced by the irradiation. No significant differences (P > 0.05) were observed for fatty acid composition, related nutritional indexes (n − 6/n − 3 and PUFA/SFA), as well as for total lipid and CLA contents, between non-irradiated (control) and irradiated meat samples. In contrast, meat irradiation affected the relative proportions of total trans, trans and cis/trans CLA isomers (P < 0.001), in addition to the percentage of some minor individual CLA isomers (t11, t13 and t9, t11, with P < 0.05 and P < 0.001, respectively). The percentage of total cis/trans CLA isomers slightly decreased in irradiated samples, while the relative proportion of total trans, trans isomers slightly increased. This observation may be explained by the higher susceptibility to autoxidation of the cis double bond relative to the trans configuration.     

冻藏时间对扇贝闭壳肌及裙边理化性质的影响

目的研究冻藏时间对华贵栉孔扇贝(Chlamys nobilis)闭壳肌及裙边理化性质的影响。方法通过测定在-18℃冻藏不同时间扇贝的基本成分、氨基酸组成、蛋白质组分、挥发性盐基氮含量及过氧化值,了解其理化性质随时间变化的规律。结果冻藏60 d的闭壳肌和裙边基本成分、水溶性蛋白、盐溶性蛋白含量和氨基酸含量变化不显著,挥发性盐基氮含量略有上升,然而过氧化值变化显著,比原来增长了81%。结论华贵栉孔扇贝在-18℃冻藏60 d,除过氧化值外,其余理化性质变化不明显。