【作者】 陈峰；

【导师】 张晓鸣；

【作者基本信息】 江南大学 ， 食品科学与工程， 2018， 硕士

【摘要】 腌制萝卜作为腌制品主要商品之一,拥有鲜艳的颜色、独特的风味与口感,一直为广大消费者所青睐。但大多数食品工厂现在仍在使用的传统腌制工艺（如干腌法）会导致萝卜在长时间的腌制储藏过程中出现严重的色泽、风味以及质构的劣变,进而影响整个产品的商品价值,每年因此造成的损失巨大。因此,对萝卜在腌制过程中的色泽、风味等品质指标的变化机制进行探索,提出一种新型且能改善萝卜在腌制过程中的品质劣变的腌制加工工艺,具有重大的实用价值,同时也能为其他蔬菜的腌制提供有效参考。本文以大根萝卜作为腌制原料,柠檬酸作为酸化剂,研究不同酸化处理方式对萝卜在腌制过程中品质的影响,其中包括不同pH酸化处理腌制、短时间传统腌制—后续长期酸化腌制以及强酸化处理—弱酸腌制等多种腌制工艺。不同pH酸化处理腌制结果显示,长期在pH 2、pH 3酸度下腌制,萝卜的色泽维持最好,但质构破坏较为严重。风味方面,气相色谱-质谱联用仪（GC-MS）结果显示腌制萝卜的挥发性物质中含硫化合物以及酯类物质的含量在风味物质中占绝对比重,是腌制萝卜的主要风味物质;腌制液pH对腌制萝卜风味物质影响巨大,随着腌制液pH的降低,腌制萝卜风味物质含量极速下降。利用偏最小二乘回归法（PLSR）对腌制萝卜风味物质与感官结果进行分析,确定了二甲基二硫、二甲基三硫、4-甲硫基-3-丁烯基异硫氰酸酯、戊二酸二甲酯、呋喃二甲酸甲酯等挥发性物质与腌制萝卜风味的显著性相关关系,其中二甲基三硫与腌制萝卜颜色呈显著正相关（p<0.05）。短时间传统腌制—后续长期酸化腌制的萝卜色泽与质构均不理想,并呈现较为严重的酸败风味,不利于萝卜的长时间腌制。采用强酸化处理—弱酸腌制工艺进行腌制,前期酸化处理测定多酚氧化酶（PPO）与硫甙葡萄糖苷酶（硫苷酶）酶活,腌制30 d后测定腌制萝卜色差变化。利用SPSS对腌制萝卜的色泽与两种酶活进行相关性分析,结果显示两种酶的活性与腌制萝卜的色泽呈极显著相关（p<0.01）。GC-MS分析结果显示萝卜的风味与前期酸化处理的pH有密切关联,而与后期腌制的初始pH关系不大。在此基础上进一步精准酸化处理,对腌制萝卜的总酚、原果胶含量、PPO与硫苷酶酶活等诸多指标进行测定并进行相关性分析。腌制萝卜的色泽与酶活显著相关（p<0.05）,证明了以色泽变化为指标,这两种酶活变化为依据的可靠性;腌制萝卜的脆度与原果胶的含量变化呈极显著正相关（p<0.01）。腌制结果显示pH 2.2、pH 2.4组均能很好地抑制萝卜的色泽劣变,添加0.4%CaCl₂能有效维持萝卜的脆度。依此对传统腌制工艺腌制成熟的萝卜进行后加工前的短期酸化处理,测定色差显示pH 2.2的酸化液能够较好地抑制加工期间传统腌制工艺萝卜色泽的劣变。对腌制萝卜料液的配方及稳定性验证和改善,并根据腌制萝卜在货架期出现的失脆褐变问题,选择添加适当的添加剂进行改善:保脆剂方面,添加0.2%的乳酸钙对萝卜质构具有很好的保护作用。护色方面,选择五种护色剂进行护色处理,在35°C恒温箱中模拟加速实验,结果显示柠檬酸和乙二胺四乙酸二钠能为萝卜颜色提供有效保护。更多还原

【Abstract】 Salted radish is one of the main products of salted products.It has bright colors,unique flavor and texture,and has been interested by consumers.However,the traditional salting process(such as dry salting)that most food factories still use today will cause severe color,flavor,and texture deterioration during the long-term salting of radish,which will affect the entire product.The result causes huge economy loss every year.Therefore,the change mechanism of color,flavor and other quality indicators in the process of salting radish is explored,and research a new type of salting processing technology of improving the quality of radish in the salting process is proposed,which has great practical significance,and it can provide an effective reference for the salting of other vegetables too.In this paper,we used white radish as salting materials,citric acid as acidifying agent,to study the effect of different acid treatment on the quality of radish in the salting process,including different pH acid salting,traditional salting combined with follow-up long-term acid salting,traditional salting before acid treatment.The results of different pH acid salting showed that long-term salting at pH 2 and pH 3 groups maintained the best radish color,but the texture were destroyed more seriously.For flavor,gas chromatography-mass spectrometry(GC-MS)results showed that the content of sulfur compounds and esters in the volatile substances of salted radish accounted for the absolute proportion of flavor substances,and which were the main flavor of salted radish.The pH of the salting solution has a great influence on the flavor of salted radish.With the decrease of salting solution’s pH,the content of the salted radish’s flavoring material decreases rapidly.The partial least squares regression(PLSR)was used to analyze the flavor and sensory results of the salted radish,and dimethyl disulfide,dimethyl trisulfide,4-methylthio-3-butenyl isothiocyanate,glutaric acid dimethyl ester and methyl furandicarboxylate were determined have a significant correlation with the flavor of salted radish.There has a significant positive correlation between dimethyl trisulfide and the color of salted radish(p < 0.05).The color,texture and flavor of radish salted by traditional salting combined with follow-up long-term acid salting are not good,which shows this method is not conducive for long-term salting of radish.Based on the above experimental results,the changes in the color of salted radish were used as an indicator,the enzyme activities of polyphenol oxidase(PPO)and glucosinolates(glucosidase)were used as the basis for the acid treatment of salted radish,which were salted by the traditional salting process after acid treatment.The correlation between the color of the salted radish and the two enzyme activities were analyzed by SPSS,and the results showed that the activities of the two enzymes had extremely significant correlation with the color of the salted radish(p < 0.01);GC-MS analysis showed radish’s flavor compounds were closely related to the pH of the previous acid treatment,and which have little to do with the initial pH of the later salting.On this basis,further accurate acid treatment was used,while the determination of PPO enzyme activity,glucosidase activity,total phenol,protopectin content and other indicators of salted radish were measured and used SPSS for correlation analysis.The color of salted radish was significantly correlated with the enzyme activity(p < 0.05),demonstrating the reliability of these two enzyme activities as acid treatment basis;the crispness of salted radish and the content of protopectin had significantlly Positive correlation(p < 0.01).The results of salting showed that the pH 2.2 and pH 2.4 groups could inhibit the deterioration of radish color well.Adding 0.4% CaCl2 can maintain crispness of radish effectively.According to the results above,the salted radish with traditional salting process were used short-term acid processing,the determination of color difference display pH 2.2 acid solution can better inhibit the traditional salting process radish color deterioration during processing.The formulation and stability of salted radish liquids were verified and improved,and according to the problem of browning and flaking of preserved radishes during shelf life,the additives were selected to improve the radish’s quality: For crispening agents,0.2% calcium lactate was added in the liquid,it has a good protective effect on radish texture.For color protection,five different color-retaining agents were selected for color protection,and accelerated experiments were performed in 35°C incubator.The results showed that citric acid and EDTA-2Na can provide effective protection for radish color.更多还原