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Developing infant milk fat similar to human milk fat (HMF) is of great interest and a challenge to food processors. In most vegetable oils used for infant milk fat production, the sn-1,3 positions of the TAGs are occupied mainly by saturated fatty acids, while in human milk these positions contain mainly unsaturated fatty acids . The location of saturated fatty acids especially palmitic acid at the sn-2 position of triacylglycerols (TAGs) increases the efficiency of absorption of fatty acids from the lumen and also decreases calcium loss in infants . Unlike vegetable oils, HMF contains about 40–60% palmitic acid at the sn-2 position of the TAGs。 Structured lipids (SLs) containing similar fatty acid structure as HMF can be produced by interesterification reactions using an sn-1,3-specific lipase that gives high selectivity and mimics the natural pathways of metabolic processes . Preliminary studies in our laboratory have revealed that enzymatic interesterification of tripalmitin with a vegetable oil blend containing coconut, safflower and soybean oils, using lipozyme RM IM as a biocatalyst, can be successful in the production of SL that mimic the fatty acid composition and structure of HMF. Safflower and soybean oils are two sources of polyunsaturated fatty acids that together with coconut oil, produces an acceptable combination of fat that can be employed in infant milk fat formulation . Furthermore, HMF contains small amounts of long chain polyunsaturated fatty acids (LCPUFAs), and the fortification of infant milk with these LCPUFAs by addition of fish oil is becoming increasingly popular for additional health benefits . However, the successful production of SLs for infant milk formulation can be impeded by their high susceptibility to oxidative deterioration. SLs or infant milks produced with lipids containing unsaturated fatty acids can deteriorate during storage and produce off-flavors and odors characteristic of oxidation . Furthermore, the production process for SLs increases free fatty acids (FFA) concentration, which is also responsible for off-flavor development . A high concentration of FFA in infant milk induces a rancid and bitter taste that is unacceptable. Also, unsaturated fatty acids in infant milk fat can be oxidized into hydroperoxides (primary oxidation products), which can then be rapidly decomposed to secondary oxidation products such as alkanes, alkenes, aldehydes, and ketones . Oxidative deterioration and high FFA concentration can alter the nutritional quality of SLs and render infant milks containing these lipids potentially toxic and unacceptable to consumers . Oxidation stability of structured lipids intended for infant milk formulation, provides insight on the acceptability of these milks for consumption. This paper therefore aims to characterize and study the oxidative stability of SLs intended as infant milk fat analogs. |
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songe0310
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【答案】应助回帖
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爱与雨下(金币+5): 2011-11-05 07:35:59
momo198548(金币+20, 翻译EPI+1): 很感激，谢谢~ 2011-11-06 19:44:40
爱与雨下(金币+5): 2011-11-05 07:35:59
momo198548(金币+20, 翻译EPI+1): 很感激，谢谢~ 2011-11-06 19:44:40
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将婴儿乳脂开发成类似于人乳脂是一件非常有趣的事情，同时这对食品加工器也是一个挑战。大多数用于生产婴儿乳脂的菜油中，三酰基甘油类成分1和3位酯键上主要是饱和脂肪酸，而人乳中则主要是不饱和脂肪酸。2位酯键上的饱和脂肪酸尤其是棕榈酸增加了儿童从官腔中吸收脂肪酸的效率，也减少了钙的流失。人乳与蔬菜油不同的是，它的三酰基甘油类成分2位酯键上含有40-60%的棕榈酸。结构脂质(SLs)可以通过采用1和3位酯键专用脂肪酶进行酯交换获得与人乳相似的脂肪酸结构，这种脂肪酶使结构脂质具有高选择性，并且其代谢过程可模拟天然的代谢途径。我们实验室的前期研究结果显示，将棕榈精与椰子油、红花油和大豆油混合，以硫辛酸酰胺RM IM为生物酶，采用酶法酯交换法能够成功得到与人乳脂肪酸成分和结构相似的结构脂质。红花油和大豆油是两种多不饱和脂肪酸类化合物的原料，它们与椰子油混合形成的脂类混合物允许添加到婴儿奶粉脂类配方中。进一步研究显示，人乳中含有少量的长链多不饱和脂肪酸(LCPUFAs)，因此为了增加奶粉的健康益处，日益流行向婴儿奶粉中添加鱼油来增加长链不饱和脂肪酸。然而，由于结构脂质非常容易氧化变质，这就阻碍了生产用于婴儿奶粉配方的该类产品的成功。用脂类制成的结构脂质或婴儿乳脂中含有不饱和脂肪酸类物质，这类物质在储存期间容易变质，并产生不良气味和氧化物的气味。进一步研究显示，结构脂质生产过程中游离脂肪酸(FFA)的浓度增加也进一步增加了异味。婴儿奶粉中游离脂肪酸浓度太高会产生一种让人难以接受的酸苦味。同样，婴儿奶粉脂类中的不饱和脂肪酸可以氧化成氢过氧化物（主要氧化产物），它们很快分解成烷烃类、醛类、酮类等次级氧化产物。氧化变质和高游离脂肪酸浓度可以改变结构脂质的营养质量，使含有这些脂类的婴儿奶粉存在潜在的毒性，并不为消费者所接受。用于婴儿奶粉配方的结构脂质的氧化稳定性促使了关于这些奶粉消费的可接受性的研究。 因此，本文旨在表征和研究婴儿乳脂的类似物-结构脂质的氧化稳定性. |
2楼2011-11-04 20:27:29