【作者】 李维；

【导师】 胡卓炎； 王莉嫦；

【作者基本信息】 华南农业大学 ， 工程硕士（专业学位）， 2018， 硕士

【摘要】 荔枝果汁的褐变,风味的劣变和营养成分的改变均与氧气存在着必不可少的联系。本文采用槐枝荔枝汁、椰子水等为原料调配成混合果汁,探讨不同预处理方式对混合果汁品质及溶解氧浓度的影响,确定了最优的预处理方式。进一步研究了该预处理方式下,溶氧量对果汁在贮藏过程中的营养成分、氨基酸组分及香气成分的影响,主要研究结果如下:(1)对比分析溶氧量、L-抗坏血酸、总酚、还原糖、γ-氨基丁酸(GABA)等含量及褐变度,酶活力。结果显示,实验条件下氮气置换处理能有效降低果汁中溶解氧含量,比抽真空处理及超声波处理的果汁溶解氧浓度更低;氮气置换处理对总酚、还原糖、GABA含量并无显著影响,对褐变指数及荔枝混合果汁中得PPO、POD酶活性无明显影响,对L-抗坏血酸含量保留率较其他两组为最高,为88.57%。氮气置换处理的混合果汁与未处理混合果汁中L-抗坏血酸含量无显著差异。(2)在果汁罐装过程中,利用氮气置换处理降低果汁初始溶解氧浓度。初始溶解氧含量分别为DO组:0.16 mg/L,CK组:5.2 mg/L。检测这两组果汁在贮藏期间的溶氧量、L-抗坏血酸、总酚、还原糖、GABA等含量及褐变度,色泽。结果显示:DO组荔枝混合果汁在贮藏过程中各营养指标均优于CK组荔枝混合果汁,氮气置换处理具有一定的积极作用。且在4℃条件下贮藏的果汁的营养指标均优于在25℃条件下贮藏的果汁,低温有助于果汁贮藏。(3)通过分析对比氮气置换联合超高压处理前后混合果汁的香气成分及氨基酸组分,结果表明:氮气处理对果汁中香气成分的流失贡献不大。超高压处理后的荔枝混合果汁氨基酸总量均稍有增加,且经过氮气置换处理的荔枝混合果汁氨基酸总量高于未处理的果汁。同时对比了贮藏前后果汁中的香气成分及氨基酸组分,结果表明:随着贮藏时间的延长,香气成分及含量,氨基酸组分及其含量均有所减少。更多还原

【Abstract】 The browning of litchi juice,the deterioration of flavor and the change of nutrient composition are all indispensable to oxygen.In this paper,the raw materials were mixed with the juice of huaizhi litchi juice and coconut water.In order to ensure the quality of different pretreatment methods,the concentration of dissolved oxygen in the fruit juice was reduced efficiently,and the optimal treatment method was selected to set different gradient dissolved oxygen content.The changes of nutrition index,amino acid composition and aroma composition in the storage process were discussed,and the main results were as follows:(1)The content of dissolved oxygen,L-ascorbic acid,total phenols,reducing sugars,γ-aminobutyric acid(GABA),browning degree and enzyme activity were compared and analyzed.The results showed that the nitrogen displacement treatment can effectively reduce the dissolved oxygen content of the juice,and the dissolved oxygen concentration of the juice was lower than that of the vacuum treatment and ultrasonic treatment.Nitrogen replacement treatment had no significant influence on total phenol,reducing sugar and GABA content.There was no obvious effect on the activity of PPO and POD in the browning index and the mixed juice of litchi,and the retention rate of L-ascorbic acid content was the highest in the other two groups,which was 88.57%.There was no significant difference in the content of L-ascorbic acid between the nitrogen-displaced mixed juice and the untreated mixed juice.(2)During the juice canning process,nitrogen substitution treatment was used to reduce the initial dissolved oxygen concentration of the juice.The initial dissolved oxygen content was DO group: 0.16 mg/L,and CK group: 5.2 mg/L.The contents of dissolved oxygen,VC,total phenols,reducing sugars,GABA,etc.,browning degree,and color of the two groups of juice during storage were measured.The results showed that: DO group litchi mixed juice in the storage process of the nutritional indicators are better than the CK group litchi mixed juice,nitrogen replacement treatment has a certain positive effect.And the nutritional index of the juice stored at 4 °C was better than that stored at 25 °C,and the low temperature was helpful for juice storage.(3)By analyzing the aroma composition and amino acid composition of mixed juice before and after nitrogen replacement + ultrahigh pressure treatment,The results showed that the nitrogen treatment did not contribute much to the loss of aroma components in the juice,and had an effect on the total amount of amino acids.The total amount of amino acids in litchi mixed juice after ultra-high pressure treatment increased significantly,and the total amount of amino acids in litchi mixed juice after nitrogen replacement treatment was higher than that of untreated juice.At the same time,the aroma components and amino acid components in the juice before and after storage were compared.The results showed that with the extension of storage time,the aroma components and content,amino acid composition and its content were all reduced.更多还原