Study On The Nitrite Control Technology And Storage Quality Of Pickles

Pickle is a traditional product of vegetables fermented by Lacto-bacteria, attracting a large number of consumers home and abroad with its unique flavor and its abundant nutrient. But there are some unsafe factors in the fermented vegetable products, the most important problem of which is excessive levels of nitrite. Nitrite can make the body abnormal, causing methemoglobinemia, more seriously, the nitrite is one of the precursor of strong carcinogen-nitrosamine, it’s very important to control the content of nitrite in pickle to improve the safety of pickle. In order to find out the effect of different conditions on nitrite content of pickle and decrease nitrite content, the raw materials of pickle, the fermentation, the kinds of LAB, the fermentation conditions and auxiliary materials were researched. And the quality of pickle during storage was also researched. The main results including:1.Through dynamic state analysis the content of nitrite in different vegetables under traditional folk processing technology, the results showed the content of nitrite increased with time accumulation during initiation fermented stage, while the content of nitrite decreased gradually during anaphase fermented stage; the nitrite peak appearance in cucumber was earlier than lettuce, Chinese cabbage, white radish and cabbage, the nitrite peak appearance in celery was the latest; The train of nitrite content peak was that: celery>lettuce>Chinese cabbage>white radish>cabbage>cucumber; when the content of nitrite was in steady state, the content of nitrite in celery was significantly higher than other vegetables’, so celery was chosen as the test material.2. Compared to natural fermentation and fermentation inoculated with old pickle brine, inoculated fermentation can significantly reduce the content of nitrite of pickle and make the speed of fermentation swiftly. Through the single-factor test, the effect of inoculated fermentation on the content of nitrite of pickle and pH of pickle brine were researched, the results showed that: Lm+Lb =1:3 and 1% inoculum was excellent vaccination agents.3. On the basis of single factor test, the optimization of nitrite minimum content was investigated using response surface methodology with three variables including fermentation temperature, sugar density and fermentation time. The regression equation was acquired:Y=3.23-0.14X₁+0.088X₂+0.50X3-0.47X₁X₂+0.91X₁X3+0.093X₂X3+1.45X₁²+0.37X₂² +1.63X32. The optimal fermentation condition were as follows: salt 5.0%, sugar 1.335%, fermentation temperature 30.5℃, fermentation time 67.68h. Under the above condition, the content of nitrite in celery pickle was 3.1807mg/kg.4. In order to remedy the shortage of the flavor of inoculated fermentation pickle, some auxiliary materials were added into the pickle. Through the single factor and orthogonal test, the optimal auxiliary materials formula was as follows: garlic 1.50%, ginger 0.50%, liquor 0.05ml/g.5. The results of fermentation of different vegetables in traditional technology and optimal technology showed that optimal technology made it possible to shorten the fermentation cycle, increase the amount of total acid and reduce the content of nitrite in pickle. The sensory indexes, physicochemical indexes and microbiological indexes of celery pickle conformed to the requirement of relative standard.6 Through dealing pickles with different sterilization and antisepsis methods, the effects of these different methods on pickle quality during storage period were compared. The results showed that: there was no change of the amount of total acid under the condition of vacuum-packed + potassium sorbate + thermal sterilization + room temperature storage, but the color, hardness and flavor went bad, the activity of LAB was lost; Under the condition of vacuum-packed + potassium sorbate + microwave sterilization + room temperature storage, the color, flavor and hardness of pickle felt good during initiation storage period, the activity of LAB also sustained with a higher level, but the color, hardness ,flavor and the amount of acid went bad in anaphase storage period; The color, hardness and a certain amount of lactic acid bacteria can be kept well under the condition of vacuum-packed + potassium sorbate + 4℃room temperature storage and vacuum-packed + 4℃room temperature storage ,there was no significant difference in the nitrite content between the two treatment groups. However, the pickle under the condition of vacuum-packed + potassium sorbate + 4℃room temperature storage was able to maintain the rich flavor. All these treatment methods can make the pickles safety for 6 months. Above all, the best sterilization and antisepsis method is: vacuum-packed + potassium sorbate + 4℃room temperature storage.