Study On The Processing Technlolgy And Quality Changes Of Low Nitrite Pickle

Pickle is a traditional food in China.The pickle made from fresh vegetables after fermentation has a unique flavor and is increasingly favored by consumers.The raw materials of pickles are easy to accumulate nitrate during the growth process and are reduced to nitrite which is harmful to human body during the fermentation process.Therefore,how to reduce the nitrite content of pickles during fermentation is very important.At present,high-salt pickles are commonly used in pickle factories for production and processing.However,there are some problems such as long processing time,high salt content,and different product quality.In this paper,mustard was used as the research object,and direct-vat fermentation was used to study the process conditions of low-nitrite pickles by adding celery extract and licorice extract.The quality changes of pickles during fermentation were studied under the optimal process,and the changes of phenolic substances and antioxidant capacity during pickle fermentation were also studied.The main results are as follows:(1)The fermentation process of low nitrite pickles was studied.The results showed that the single factor test showed that the nitrite content in pickles was the lowest when the amount of celery extract was 8 %,licorice extract was 6 %,and salt was 5 %.The optimal fermentation conditions of pickles obtained by response surface optimization test were as follows: the addition amount of celery extract was 9.2 %,licorice extract was 6.8 %,salt was 4.6 %,and the fermentation time was 8 days.Under these conditions,the nitrite content in pickles was the lowest,which was 6.776 mg/kg.(2)The quality changes of low nitrite pickles during fermentation were studied by adding extracts.The results showed that the p H and total acid content of low nitrite pickles at the end of fermentation were 3.89 and 0.23 g / 100 g,respectively.The nitrite content in pickles at the end of fermentation was lower than the safety level of national food safety standards(20 mg /kg),and the nitrite content in low nitrite pickles decreased by 35.66 %.Low nitrite pickles had better color during fermentation.At the end of fermentation,the hardness,crispness and chewiness of pickle samples decreased compared with raw materials.In sensory evaluation,low nitrite pickles were better in color,aroma and taste,and there was no significant difference in texture(p > 0.05).(3)Study on the changes of flavor components during fermentation.The changes of volatile flavor substances in pickle samples at the early stage(0d),middle stage(4d)and late stage(8d)of pickle fermentation were studied.104 types of substances were detected in the samples,of which 53 compounds were detected in the raw materials.In the CK group,55 and53 compounds were detected on the 4th and 8th days of fermentation,respectively.In the experimental group,54 and 57 compounds were detected on the 4th and 8th days.The results showed that the content of isothiocyanates in low nitrite pickles decreased,the pungency of the taste decreased,and the content of other esters increased,which enriched the flavor of low nitrite pickles.The relative contents of alcohols,ketones,aldehydes,olefins and phenols were higher than those in the CK group,while the relative contents of other compounds were lower.There was no significant difference in acid compounds between the two groups,indicating that low nitrite pickles had better flavor.(4)The changes of total phenols,total flavonoids,DPPH free radical scavenging rate and iron ion reducing power of pickles during fermentation were studied.The results showed that the contents of total phenols and total flavonoids in low nitrite pickles at the end of fermentation were significantly different from those in the CK group(p < 0.01).At the end of fermentation,the DPPH free radical scavenging rate of the CK group and experimental group was significantly different(p < 0.01),and the antioxidant capacity of low nitrite pickles was significantly improved.There was no significant difference in ion-reducing power between the CK group and experimental group at the end of fermentation(p > 0.05),but the difference was significant compared with raw materials(p > 0.05),indicating that fermentation could improve the iron ion reducing power of pickles.Correlation analysis showed that the contents of total phenols and total flavonoids in pickles during fermentation were positively correlated with DPPH free radical scavenging rate and iron ion reducing power.