Study On Food Processing And Quality Control Technology Of Fermented Mandarin Fish

Fermented mandarin fish,as a traditional solid-state fermented fish product,is popular in Southern Anhui,China.It not only retains the rich nutrients in aquatic products,but also has special flavor.In recent years,with the increase of consumption heat of fermented mandarin fish product,the demand is greatly increased and the requirements for product quality are also raised.However,fermented mandarin fish is still processed by empirical and traditional natural fermentation technology.The low degree of intensification of processing enterprises,single equipment and unstable flavor of products restrict the industrialization and standardized development.It is necessary to promote product innovation and industrial upgrading through the application of new process and new technology.Inoculating starter is one of the hot research topics for improving and stabilizing the quality of fermentation products.Therefore,on the basis of understanding the flavor quality and microbial composition of traditional fermented mandarin fish,this paper selected suitable strain starters,and then developed a new fermented mandarin fish product using artificial directed inoculation fermentation technology,and explored the influence of inoculation fermentation on the quality of fermented mandarin fish.The main research were as follows:(1)Using solid phase microextraction(SPME)combined with gas chromatography-mass spectrometry(GC-MS)and relative odor activity value(ROAV),the volatile flavor compounds of mandarin fish during traditional fermentation were identified and analyzed.A total of 64 flavor substances were detected during fermentation,including27 hydrocarbons,10 alcohols,4 aldehydes,4 ketones,3 acids,4 esters,9 aromatic,and 3nitrogen and sulfur compounds.Most of the volatile substances were formed during fermentation,alcohols,nitrogen compounds,aldehydes and esters were important flavor compounds.Combined with ROAV,linalool,1-octene-3-ol,hexanal,decanal,nonanal,trimethylamine(TMA),geranyl acetate,d-limonene and other volatile compounds contributed significantly to overall flavor of fermented mandarin fish.The formation of these compounds came from the degradation of amino acids,biochemical reactions such as lipid hydrolysis and oxidation,and the introduction of spices.The ROAV of linalol,1-octene-3-ol,nonanal,TMA and other flavor substances were greater than 10,which had significant influence on the unique flavor of fermented mandarin fish.(2)Elucidate the changes of microbial community succession and diversity of mandarin fish during traditional fermentation.The analysis of microbial community structure in the fermentation process of fermented mandarin fish by high-throughput sequencing technology.The results showed that the microbial diversity of fermented mandarin fish presented a dynamic trend of decline and the difference of bacterial community structure gradually decreased during fermentation.A total of 20 phylum and 16 genera were detected in the whole fermentation,among which 62 species participated in the whole fermentation.Proteobacteria and Fusobacteria were the most important phylum in the whole fermentation of mandarin fish.Psychrilyobacter,Fusobacterium,Acidaminococcus,Psychromonas,Vibrio,Sulfurimonas and Arcobacter were important dominant microorganisms.Psychrilyobacter were dominant in the early and middle stages of fermentation,while Fusobacterium played a dominant role in the middle and late stages of fermentation.Based on Pearson correlation analysis,the potential relationship between microorganisms and key flavor compounds of fermented mandarin fish was investigated.It was found that Psychrilyobacter,Fusobacterium,Acidaminococcus,Sulfurimonas and Arcobacter were positively correlated with many key flavor compounds,such as linalols,TMA,1-octene-3-ol and so on,which played an important role in the formation of characteristic flavor.(3)Selection and characteristic analysis of mixed strain starter.With Pediococcus pentosaceus,Pediococcus acidilactici,Lactobacillus sakei and Staphylococcus carnosus as research objects,they all reached the stable growth period within 24 h.The acid production capacity of Lactobacillus sakei was strongest,while that of Staphylococcus carnosus was weakest.The four strains all showed strong activity at 4% salt concentration,and salt tolerance of Lactobacillus sakei and Staphylococcus carnosus was 6% and 8%,respectively.The growth capacity,acid production capacity and salt tolerance of Pediococcus pentosaceus and Pediococcus acidilactici were similar.The four strains all had protease activity and have no antagonism among strains,and could be prepared for the fermentation research of mandarin fish.The moisture,pH,texture and sensory quality of each group were determined.The results showed that when the mixed strain starter was Pediococcus pentosaceus,Lactobacillus sakei and Staphylococcus carnosus,the moisture and pH of fermented mandarin fish could be effectively reduced,and the product had good quality and texture and sensory quality.(4)Study on the fermentation process of mandarin fish based on mixed strain starter.The fermentation temperature,fermentation time,strain ratio,and inoculation amount of starter were taken as the main conditions for the process optimization of fermented mandarin fish.Firstly,the optimal range of each factor was determined by single factor test.Then,response surface tests were used to optimize the fermentation conditions of mandarin fish,including fermentation temperature,fermentation time and inoculation amount.The optimal fermentation conditions were obtained as follows: The strains ratio of Pediococcus pentosaceu: Lactobacillus sakei: Staphylococcus carnosus=1:1:3,fermentation temperature 21.54 ℃,fermentation time 3.83 d,inoculation amount 1.04%,sensory score 85.03 points.Meanwhile,considering the actual production demand,the optimal fermentation process was adjusted as: The strains ratio of Pediococcus pentosaceu:Lactobacillus sakei: Staphylococcus carnosus=1:1:3,fermentation temperature 22 ℃,fermentation time 4 d,inoculation amount 1.0% and sensory score 84.30 points.The experimental result was close to the theoretical data.(5)Development and quality analysis of inoculated fermented mandarin fish product.The mandarin fish was fermented under the optimum fermentation conditions to study the effect of inoculated fermentation on the quality of fermented mandarin fish.Compared with the natural fermented mandarin fish,the moisture and pH of inoculated fermented mandarin fish sample decreased.The proteolytic effect of inoculated fermented samples was obvious,its amino nitrogen content was similar to that of natural fermented mandarin fish.The total acid content was higher than that of natural fermented mandarin fish.However,the contents of TBA and TVB-N were significantly decreased,and the lipid oxidation and protein degradation could be inhibited by inoculated fermentation.Compared with the fresh mandarin fish,the microscopic structure of inoculated fermented mandarin fish changed significantly,and was similar to the natural fermented mandarin fish.Additionally,The microorganism on the surface of muscle fiber of inoculated sample was more uniform.Inoculated fermented mandarin fish could produce a variety of volatile flavor components,such as alcohols,esters,aldehydes,ketones,acids,hydrocarbons and so on,in a short fermentation.The content of linalool was close to that of natural fermented mandarin fish.The "smelly" substances such as TMA and indole were significantly reduced,and the overall flavor of fermented mandarin fish presented a light smelly flavor,which was more acceptable to consumers and improved the safety of the product.