| In the production process of low salt pickled Chinese cabbage,in order to effectively extend its shelf life,sterilization technology is particularly important.Due to the advantages of cold sterilization,irradiation sterilization technology has gradually been applied to the processing and preservation of agricultural products such as fruits,vegetables,and grains.On the basis of the previous research on the irradiation treatment of pickled Chinese cabbage,this study used quality indicators and metabonomics analysis to explore the impact of two irradiation resistant microorganisms(Bacillus megaterium and Pichia pastoris)on the quality of pickled Chinese cabbage,understand the changes of irradiation resistance of irradiation resistant microorganisms under the action of different barrier factors(salt,p H,sugar,preservatives),and obtain the irradiation combined preservative sterilization process.The main research results obtained are as follows:1.Effects of inoculating radiation tolerant microorganisms on the quality of pickled Chinese cabbage.The crispness,hardness and chewiness of pickled Chinese cabbage group inoculated with irradiation resistant microorganisms decreased significantly,and Pichia pastoris had a greater impact on the texture characteristics of pickled Chinese cabbage.During the storage period,the color of pickled Chinese cabbage becomes darker,brownish and worse.The aroma components such as esters and ketones in pickled Chinese cabbage were reduced,and some hydrocarbons with typical putrid smell were detected.In general,Bacillus megaterium and Pichia pastoris have adverse effects on the quality of pickled Chinese cabbage,which are putrefactive microorganisms in pickled Chinese cabbage.2.Metabonomic analysis of pickled Chinese cabbage inoculated with radiation tolerant microorganisms.After inoculation of irradiation resistant microorganisms,60 substances in pickled Chinese cabbage were up-regulated,most of which were amino acid metabolites,organic acid derivatives,flavonoids and other substances,such as some glucosides,phenylacetone and so on.There are 23 substances that are downregulated,mainly amino acids,lipids,and lipid molecules,such as alanine,glycerol phospholipids,and other substances.It showed that the characteristic flavor substances such as organic acids and amino acids in pickled Chinese cabbage were degraded largely after inoculation of irradiation resistant microorganisms.3.The effect of different barrier factors on the irradiation sterilization effect of radiation resistant microorganisms.The low acidic environment has a certain synergistic effect on the irradiation killing of Bacillus megaterium,but it has no significant effect on Pichia pastoris;In 1%～7% sugar solution,it has antagonism on irradiation sterilization,and when sugar concentration is more than 7%,it has synergistic effect on irradiation sterilization;1%～9% salt solution has a synergistic effect on the irradiation killing of both strains of bacteria.In addition,the inhibitory effect of different preservatives on Bacillus megaterium was in the order of Nisin>potassium sorbate>sodium benzoate,and the inhibitory effect on Pichia pastoris was in the order of potassium sorbate>sodium benzoate>Nisin.4.Effects of compound preservatives combined with irradiation sterilization on the quality of pickled Chinese cabbage.The response surface methodology was used to determine the optimal formulation of a composite anti-corrosion agent: potassium sorbate added at 0.05 g/kg,sodium benzoate added at 0.5 g/kg,and Nisin added at0.13 g/kg.The results of comparison between single heat sterilization and combined sterilization showed that the crispness,hardness and chewiness of pickled Chinese cabbage decreased when the traditional heat sterilization method was used alone;The content of nitrite is greatly reduced;The organic acid content has increased,especially in oxalic acid and lactic acid,with a sensory score of only 75 points,but the sterilization effect is good.When the preservative is combined with 2～3 k Gy,the bactericidal effect is good,and the texture and color of pickled Chinese cabbage are good,the volatile flavor substances are rich,and the highest sensory score is 85 points. |
