Research On The Browning Effect And Regulation Technology Of Pickled Peppe

Pickled pepper is processed with fresh pepper as raw material,and is also an important fermented vegetable products and condiments for daily table,with bright color,fresh and tender,sour and spicy,etc.It is one of the commonly used auxiliary ingredients in Yunnan,Guizhou and Sichuan cuisine at present.At present,the production of pickled pepper mainly adopts traditional technology methods,fermentation and storage process of fading and browning problems have not been effectively solved,browning occurs after the pickled pepper commodity value decreased significantly,shelf life and market competitiveness is reduced.At present,there is a lack of in-depth research on the problem of browning of pickled pepper,and there is also a lack of scientific and effective control technology for its browning.Therefore,this thesis analyzes the browning and its influencing conditions during the fermentation and storage of pickled pepper,investigates the main causes of browning and the ways of browning control during the fermentation and storage of pickled pepper,and analyzes and evaluates the flavor quality of pickled pepper after the inhibition technology to provide effective technical means for the browning control of pickled pepper.The main research results are as follows:(1)The study firstly investigated the effects of fermentation temperature,salt,sugar and white wine on the fermentation browning degree of pickled pepper,and optimized their process conditions.The results showed that the main order of browning influencing factors of pickled pepper was temperature > salt > sugar >white wine,i.e.,the browning degree of pickled pepper was 8.07 when fermented at6% white wine,12% salt,2.5% white sugar and 20℃,which was 31.03% lower than that of the control group.On this basis,the effect of different anti-browning agents on the browning degree of pickled pepper was investigated,and the best formulation of anti-browning agent was determined by TOPSIS method as 0.2% chitosan,0.15%sodium D-isoascorbate and 0.1% γ-aminobutyric acid.Compared with a single antibrowning agent,the browning degree was reduced by 11% to 44% and the sensory score was optimal.In addition,the browning of fermented pickled peppers fortified by Lactobacillus acidophilus GIM.1.208(16.37)decreased significantly(p < 0.01)compared with the control(24.98)and reduced the loss of reducing sugars,ascorbic acid,total phenols and amino acid nitrogen,as well as the accumulation of malondialdehyde(MDA)during the fermentation process.The Spearman correlation analysis showed that the browning degree of pickled pepper was highly significantly negatively correlated with total phenols,reducing sugars and ascorbic acid(p < 0.01)and highly significantly positively correlated with amino acid nitrogen and MDA(p <0.01).(2)In order to investigate the main causes of browning and browning regulation pathways in pepper,the physical and chemical indicators related to pepper browning were analyzed in combination with non-targeted metabolite histology.The results showed that the browning degree of pickled pepper increased gradually with time,and the activities of pickled pepper polyphenol oxidase(PPO)and peroxidase(POD)in the anti-browning agent group(KF)and Lactobacillus acidophilus group(AF)were significantly reduced.Phenylalanine aminolase(PAL)activity increased in the control group(CK)and AF,and PAL activity was significantly inhibited in the KF group,and total phenol,reducing sugar,and ascorbic acid contents were higher in the AF and KF groups than in the CK group after fermentation.A total of 1004 metabolites were detected by metabolomics techniques,and the number of metabolites differed between AF and CK and KF and CK were 64 and 59,respectively.Most of them were amino acids and their derivatives and fatty acids,as well as a small amount of flavonoids and phenolics.The results of the differential metabolite enrichment pathways in each group showed that the browning of L.foetida mainly originated from the interaction of enzymatic browning and lipid peroxidation reactions.It was also found that Lactobacillus acidophilus modulated the browning of pickled pepper highly correlated with arachidonic acid metabolism,pyrimidine metabolism,valine,leucine and isoleucine biosynthesis and phenylpropane biosynthesis pathway,and Lactobacillus acidophilus activated pickled pepper phenylalanine aminolyase(PAL)activity to induce flavonoid and phenolic compound accumulation,while inhibiting polyphenol oxidase(PPO)and peroxidase(POD)activities.The enzymatic reaction between browning enzymes and substrate phenols was reduced,resulting in increased antioxidant activity of pickled pepper,and possibly reducing unsaturated fatty acid metabolic reactions induced by cyclooxygenases(COX)and lipoxygenases(LOXs),slowing down lipid peroxidation reactions and protecting cell membrane structures,thus inhibiting browning reactions.Studies have shown that anti-browning agents reduce browning reaction substrates by inhibiting PPO and POD activity during fermentation thereby inhibiting PPO-and POD-induced enzymatic browning by the action of phenolic compounds in pickled pepper,and inhibiting PAL activity and reducing the accumulation of phenolic substances,and the inhibition of browning reaction is mainly based on the regulation of benzyl propane biosynthesis and arachidonic acid metabolic pathway.(3)Using headspace solid-phase microextraction gas chromatography-mass spectrometry(SPME-GC-MS)combined with electronic tongue technology,the characteristics and differences of volatile flavor compounds in pickled peppers under different anti browning treatments were analyzed,and the effect of anti browning treatment on product flavor quality was explored.The results showed that the taste difference of four pickled peppers could be directly distinguished by electronic tongue radar atlas combined with PCA and OPLS-DA analysis.The taste difference of CK,AF and KF was significant compared with that of unfermented(NF),and the taste difference of CK and AF was smaller than that of KF.The SPME-GC-MS detection results showed that compared with NF,CK,AF,and KF detected ethers and sulfurcontaining compounds that imparted the aroma of pickled peppers.Among them,the content of ethyl acetate in AF and KF increased significantly.Aldehydes,ketones and other substances metabolized by unsaturated fat acids were detected in CK,AF and KF,which confirmed that lipid peroxidation occurred in pickled peppers during fermentation.(E)-2-heptene aldehyde in CK is prone to Maillard reaction with amino group to promote browning,while aldehyde and ketone substances detected in AF and KF are acetoin α-Violet ketone and dihydrogen-β Aroma contributing substances such as ionone.The results showed that the treatment of pickled peppers with Lactobacillus acidophilus and anti browning agents not only inhibited browning,but also had a good effect on enhancing and improving their flavor.