蛋白预涂油膜对营养棒储藏品质的影响

Quality improvement of high-protein nutrition bars during storage by pre-coating of protein with coconut oil

目的为改善高蛋白营养棒的储藏稳定性,研究了乳蛋白预涂油膜对营养棒硬化及色变的改善效果,并探讨了可能的机制。方法将高蛋白营养棒分为对照组和预涂层组,两组都放于37℃恒温箱中储存35 d,定期取出样品,并对其硬度、色差、有效赖氨酸、游离巯基进行监测及电泳分析蛋白变化。结果相对于对照组样品,预涂层营养棒储存35 d后硬度增加及亮度降低分别减少了24.14%和11.55%,尤其储藏初期,硬化速度明显低于对照组(P<0.05)。游离巯基保留率显著高于对照组12.11%(P<0.05),表明蛋白质间分子交联程度弱。对于有效赖氨酸保留率,预涂层组亦明显高于对照组5.21%(P<0.05),表明其美拉德反应部分受到抑制,因此产品颜色保持较好,此外因美拉德反应引起的蛋白聚合、棒硬化得以改善。结论蛋白预涂油层对于改善高蛋白营养棒储存质量是有效的,其机制可能是通过减缓蛋白之间的交联及蛋白与还原糖之间的美拉德反应来实现的。

Objective To improve the quality of high-protein nutrition bars during storage,impact ofpre-coating of protein with coconut oil on hardness and color were studied,and the possible mechanism was explored in this study.Methods The high-protein nutrition bars were divided into two groups：the control and the coated,both of them were put in an incubator chamber at 37 ℃ for 35 days.During the storage,the bars were taken out regularly and measured the hardness,color,reactive lysine,free sulfhydryl group,as well as the SDS-PAGE.Results The hardness increase and L＊ decrease could be reduced by 24.14% and 11.55% compared with control when coated samples stored for 35 days.The improvement is especially significant at the early stage of storage.There was a 12.11% decrease for free sulfhydryl group loss in experimental group,which verified the decrease of the intermolecular cross-linking by protein coating.As for the reservation of free reactive lysine analysis,the loss of reactive lysine of the coated was 5.21% less than the control,which suggested Maillard reaction was suppressed to some extent,so the products kept fit color after storage.In addition,the protein aggregation and bars hardening caused by Maillard reaction were improved.SDS-PAGE showed that the degree of protein aggregation and denaturation was lower compared to the control.Conclusion The improvement of the high-protein bars storage quality by pre-coating of protein with coconut oil was effective.It was accomplished possibly through protecting the proteins from the cross-linkage and the Maillard reaction between the proteins and reducing sugars.