【作者】 李倩；

【导师】 尉立刚；

【作者基本信息】 山西大学 ， 食品科学与工程， 2021， 硕士

【摘要】 晚期糖基化终末产物(Advanced glycation end-products,AGEs)可由还原糖的羰基与蛋白质、多肽、氨基酸等物质的游离氨基经过复杂的反应而生成,是一类化学结构稳定且对人体有害的物质。AGEs主要产生于人体的自身代谢及饮食摄入。为减少AGEs对人体的危害,深入研究食品中AGEs的产生机制具有现实意义。肉及其制品是高脂高蛋白的典型代表,是膳食中AGEs的重要来源。低温冻藏,由于其经济性和便捷性,在肉类工业中的应用非常普遍。然而,肉类冻藏时蛋白或脂肪氧化不可避免,会影响肉及其制品中AGEs的形成。因此,本文以肉及其制品为研究对象,研究冻藏时间对猪肉中肌原纤维蛋白(Myofibrillar proteins,MPs)、MPs凝胶及肉丸中AGEs生成的影响,旨在明确肉制品中AGEs的生成机制,为减少肉制品中的AGEs提供理论依据。主要研究内容及结果如下:(1)冻藏时间对猪肉中MPs氧化程度的影响。对在-18℃下储藏不同时间(0、1、4、8、12周)的猪肉进行MPs提取,对其羰基、总巯基、自由氨基、表面疏水性和内源性色氨酸荧光进行测定。结果表明:随着储藏时间的延长,羰基含量显著升高(P<0.05),总巯基、自由氨基、表面疏水性和内源性色氨酸荧光强度整体呈下降趋势(P<0.05);储藏时间与羰基、总巯基、自由氨基或表面疏水性之间具有显著相关性。因此,即便在冻藏条件下,MPs也会出现一定程度的氧化,导致猪肉品质下降。(2)冻藏时间对MPs凝胶性能的影响。将猪肉进行低温冻藏(-18℃,0、1、4、8、12周),提取MPs,然后通过热诱导制成MPs凝胶,对MPs中残余脂肪的硫代巴比妥酸(Thiobarbituric acid-reactive substances,TBARS)值、MPs溶解度、凝胶保水性、凝胶白度及强度进行测定。结果表明:随着储藏时间的延长,TBARS值总体呈上升趋势;MPs溶解度、凝胶保水性、白度及强度均呈下降趋势。因此,即便将猪肉进行了低温冻藏,MPs依旧发生了氧化,进而显著影响了MPs的凝胶特性。(3)猪肉冻藏对肉丸中AGEs形成的影响。将在-18 ~oC下冻藏不同时间(0、30、60、90、120天)的猪肉制成肉丸,测定肉丸中羧甲基赖氨酸(N~ε-(carboxymethyl)lysine,CML)和羧乙基赖氨酸(N~ε-(carboxyethyl)lysine,CEL)的含量。结果表明:随着储藏时间的延长,肉丸中的CML从13.26(0天)增至43.30mg/kg protein(120天),CEL从12.37(0天)升至40.50 mg/kg protein(120天)。此外,进一步评估了猪肉冻藏过程中的氧化损伤情况(羰基、总巯基、自由氨基、表面疏水性、残余脂肪中的硫代巴比妥酸值、内源性色氨酸荧光),发现MPs氧化与CML及CEL含量之间有显著的相关性,表明冻藏过程中猪肉的氧化损伤能够促进肉丸中CML及CEL的形成。因此,在原料肉冻藏时控制MPs的氧化可以减少肉丸中AGEs的生成。更多还原

【Abstract】 Advanced glycation end-products(AGEs),reaction products of amino groups with carbonyl compounds,are substances with stable chemical structure and harmful to human health.AGEs are formed mainly by the body’s metabolism and dietary intake.In order to reduce the harm of AGEs to human body,it is meaningful to research the formation mechanism of AGEs in foods.As a good source of nutrients,such as protein and fat,meat was often selected to study AGEs in meat and meat products.Frozen storage is common in the meat industry due to its economy and convenience.Usually,raw pork used in meat products is often frozen at-18 ~oC for long periods of time,which inevitably leads to protein or lipid oxidation.However,different levels of oxidized protein or lipid showed vary effects on AGEs formation in meat products.Therefore,the objective of this study was to investigate the effects of frozen storage time of raw pork on the physical and chemical indexes of myofibrillar proteins(MPs),properties of myofibrillar protein gels and the generation of AGEs in meatballs.The results could be used to research the formation mechanism of AGEs in meat products,thereby providing a theoretical reference for reducing the intake of dietary AGEs.The main contents and results of this study are as follows:(1)Effect of frozen storage time on the oxidation degree of porcine MPs.Raw pork was stored at-18℃for different time(0,1,4,8,12 weeks),and used for the extraction of MPs.Then protein oxidation parameters(carbonyl,total sulfhydryl group,free amino groups,surface hydrophobicity and endogenous tryptophan fluorescence)were determined.The results suggested that,carbonyl content increased significantly(P<0.05),and total sulfhydryl group,free amino groups,surface hydrophobicity and endogenous tryptophan fluorescence content generally showed a decreasing trend(P<0.05).There is a correlation between storage time and carbonyls,total sulfhydryl group,free amino groups or surface hydrophobicity.Therefore,MPs will be oxidized during the frozen storage,resulting in the degradation of raw meat quality.(2)Effect of frozen storage time on properties of myofibrillar protein gels.Raw pork was stored at-18℃for different time(0,1,4,8,12 weeks),and used for the extraction of MPs and preparation myofibrillary protein gels.The properties of myofibrillar protein gels were investigated by measuring thiobarbituric acid-reactive substances(TBARS),solubility of MPs,water-holding capacity of myofibrillar protein gels,whiteness of myofibrillar protein gels and strengths of myofibrillar protein gels.The results suggested that,TBARS value increased,and solubility of MPs,water-holding capacity of myofibrillar protein gels,whiteness of myofibrillar protein gels and strengths of myofibrillar protein gels showed a decreasing trend.Therefore,MPs were oxidized during the frozen storage,which significantly affected properties of myofibrillar protein gels.(3)Impact of frozen storage duration of raw pork on the formation of advanced glycation end-products in meatballs.Meatballs were prepared using frozen raw pork(-18 ~oC,0,30,60,90 and 120 days),and N~ε-(carboxymethyl)lysine(CML)and N~ε-(carboxyethyl)lysine(CEL)(typical AGEs)were determined.The results suggested that,CML contents in meatballs increased from 13.26(0 day)to 43.30 mg/kg protein(120 days),and CEL levels increased from 12.37(0 day)to 40.50 mg/kg protein(120days)with the increasing frozen storage time of raw pork.Furthermore,oxidative damages of raw pork(carbonyls,total sulfhydryl groups,free amines,the surface hydrophobicity,TBARS of residual lipids and intrinsic tryptophan fluorescence intensity)were assessed during frozen storage.A significant correlation between MPs oxidation and CML/CEL contents was observed,which indicated that oxidative damages to raw pork during frozen storage could promote the generation of CML and CEL in meatballs.Therefore,control of MPs oxidation in raw pork may facilitate the reduction of AGEs generation in meatballs.更多还原