| The aquatic resources of china are rich and the harvesting period is concentrated. Because of the structural characteristic of jellyfish itself, autolysis is easily occurred if not timely post-harvest processed. The traditional method is pickled repeatedly by lots of salt and alum. Although prolonged the preservation of jellyfish and maintained the structure of the organization, it’s not convenient to eat. Complexed desalting step is needed, which is unable to meet the current consumer’s demand for ready-to-eat food. The ready-to-eat jellyfish, furthered processed traditional desalted and dealumed jellyfish, can meet the need to eat instantly but in order to improve the storage effect, but in the same time preservatives are heavily added.Lactobacillus is essential for the human body and importantly physiological function flora. As a gram-positive bacteria, it is capable of binding to carbohydrate and produce lactic acid by fermentation. The acid can inhibit the growth of microorganisms in food mainly. Adding lactic acid bacteria to the food and making it a competitive advantage flora will inhibit the growth of harmful microbes. Therefore, it can play a preservation effect if we add lactic acid bacteria to aquatic product and maintain a certain number of viable cells.In this study, we chose desalted and dealumed jellyfish as experimental subjects to study effect of the addition of lactic acid bacteria to preservation of jellyfish. Lactobacillus was added to samples, and control was set. Sensory indicators and physical and chemical indicators were used to test the effect. Main content was divided into three parts: 1. Process optimization of addition lactic acid bacteria to jellyfish. 2. Research of addition of lactic acid bacteria to the effect of quality of jellyfish. 3. Research of addition of lactic acid bacteria to the effect of shelf life of jellyfish. The main results are described as follows:1. Basic components of jellyfish were focused on the contents of moisture, protein, ash, salt and amino acids. The results implied that the ash content of salted jellyfish(wet basis) and desalted jellyfish(wet basis) were 1.42% and 1.33% respectively. Water content were 59.2% and 93.1%, protein content were 1.56% and 1.50%, salt content were 35.6% and 2.33%. According to the analysis of amino acids component and content of salted and desalted jellyfish, 17 essential amino acids were detected, excepted for tryptophan and ammonia. The total percentage of essential amino acids in total amino acids were 29.35% and 29.68%. Besides, the total percentage of delicious amino acids in total amino acids were 27.13% and 26.88%. Adding lactic acid bacteria to the desalted jellyfish, single factor experiment and response surface experiment were applied to study the optimal reaction parameters. The optimal reaction factors: fermentation temperature was 37 ℃, fermentation time was 35 h, the amount of lactic acid compound was 6%, the proportion of Lactobacillus inoculated with Lactobacillus brevis was 2: 1.2. According to the detection of physical and chemical indicators and microbiological test, addition of lactic acid bacteria to the desalted jellyfish was of a preservative effect. After adding to the jellyfish, Lactobacillus was always in a dominant state and the series of magnitude difference between the total number of lactic acid bacteria colonies and the number of whole colonies was significantly less than the untreated groups. This implied that the process can effectively inhibit the growth of contaminating bacteria and improve the storage quality of desalted jellyfish. The physical and chemical properties(drip loss, toughness, sensory quality, free amino acid content) of treated jellyfish were better than untreated groups. The results obtained by scanning electron microscopy showed the addition of lactobacillus can well maintain the physical configuration.3. TPA, electronic tongue principal component analysis, the number of microbial testing and sensory quality assessment analysis were applied to the desalted jellyfish at 4℃ storage environment with different storage time. It could be inferred through TPA analysis that the hardness of treated desalted jellyfish was repeated from 20 d to 40 d, the hardness of control groups were reduced in the progress. The plastic viscosity and chewiness of the two groups were showing decreased during the storage time from 0d to 40 d. According to the electronic tongue principal component analysis, the principal components of the desalted jellyfish added lactobacillus were less obviously changed from 0d to 30 d. It began to vary from 30 d, and significantly changed from 40 d while the change of control groups were more obvious from 0d to 60 d. Owing to the microbe detection, the number of lactobacillus of treated groups began to decrease from 40 d while the lactobacillus of control groups were decreased after 30 d and the number of total colonies were increased. The detection results of the sensory evaluation of the quality of desalted jellyfish indicated that the senses value of taste and smell of treated desalted jellyfish were less than 5 points after storage 30 d. The same indicators in control groups appeared at 20 d. Thanks to that, we declared that the shelf life of desalted jellyfish added of lactobacillus was 30 days in the 4℃ storage environment, the control group was 20 days. |
