我们报道，据美国营养成分网消息，目前一项新的研究已对酸奶中具有抗氧化能力的蛋白成分进行鉴定和测序。而这种蛋白具有在功能性食品中作为稳定剂的应用前景。我们今年8月5日，对“酸奶蛋白可防止ω- 3氧化”的研究发现进行了报道，而我们要现在介绍的这篇研究报告为上述报道的后续研究。
这篇研究论文仍然是发表在《食品化学》期刊上。这项来自丹麦哥本哈根大学的研究人员所进行的研究针对酸奶中那些具有抗氧化活性的蛋白进行了进一步的研究。氨基酸的含量、排序、以及肽的表征赋予这些蛋白抗氧化的活性，而这些信息的获得则可以用来合成及纯化具有抗氧化活性的蛋白，并把这些蛋白添加到食物中，使食物具有类似天然的抗氧化活性。
这项研究发现，所有以前被发现具有抗氧化活性的肽段中都有脯氨酸残基，这一发现支持以前的研究表明抗氧化活性可能与含有脯氨酸有关。大量的抗氧化肽也被发现在N -端含有疏水氨基酸亮氨酸或缬氨酸残基，与以往的研究结果一致，这与抗氧化剂有很大的关系。此外，酸奶中的游离氨基酸（组氨酸，酪氨酸，蛋氨酸和半胱氨酸），已被报道具有很强的抗氧化性能。
原文报道：
Yogurt proteins could stabilize omega-3 enrichment
By Nathan Gray, 29-Jul-2010
Related topics: Omega-3, Research, Antioxidants, carotenoids, Nutritional lipids and oils, Proteins, peptides, amino acids
New research suggests that naturally occurring antioxidant peptides could be used to prevent oxidation of omega-3 in functional foods.
Adding omega-3 rich fish oils into functional food products by substituting it for some of the original fat in foods could be a way to increase the amount of long chain omega-3 in our diet. However the problems involved with incorporating fish-oils in food products are well established. The main problem with introducing fish oils such as omega-3 to into food products is that it brings oxidative instability and can lead to potential ‘off-flavor’ formation.
Research that assessed the feasibility of such enrichment in dairy products found that yogurt with added omega-3 fatty acids are less susceptible to oxidation then milk containing the same amount of omega-3.
The new study, reported in the journal Food Chemistry, aimed to investigate the reason for such big differences in oxidative stability, with differences suggested to be due to the different protein composition of milk and yogurt.
The research measured the antioxidant properties of protein fragments formed when milk is fermented into yogurt. Samples of yogurt proteins of various sizes (3kDa, 10kDa, and 30 kDa), were tested for antioxidant activity by investigating DPPH radical-scavenging activity, Fe2+ iron-chelating activity, and reducing power.
The study observed that the smaller fraction peptides (<10kDa) were more effective antioxidants than larger fractions, especially in terms of Fe2+-chelanting activity and reducing power – of which Fe has previously been suggested to be important catalyst in fish-oil oxidation.
The smaller proteins with high antioxidant properties were then tested in omega-3 enriched milk which usually has a low oxidative stability, and were found to offer protection against oxidation of fish-oil enrichments.
The study’s findings suggest that the higher oxidative stability of yogurt might be due to antioxidant peptides released during the fermentation of milk by lactic acid bacteria, and that these peptides could be used to offer oxidative stability to fish-oil enriched food products.
Further work is now needed to identify exactly which peptides have the observed benefits on oxidative stability. The researchers wrote: “Since the antioxidant activity of the peptides depends on amino acid compositions, sequence and configuration of peptides, we cannot explain the exact mechanism for the observed findings”
Further purification and characterization of these [protein] fractions may offer an explanation for the discrepancies in the active peptides”.
With indications that current diets are highly deficient in omega-3 fatty acids, the greater oxidative stability provided by adding natural antioxidant peptides to an omega-3 enriched functional food could make omega-3 enrichment in foods more straightforward.
The study concludes: “These results also demonstrate the applicability of these naturally-occurring antioxidant peptides as an ingredient in foods enriched with fish oils to increase their oxidative stability.”
原文地址：http://www.nutraingredients-usa.com/On-your-radar/Omega-3/Yogurt-proteins-could-stabilize-omega-3-enrichment
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