| Pomegranate is rich in nutritional value,green skin soft seed pomegranate is one of the main planted variety in Sichuan Huili,and the planting area is up to 20000 hm2,the yield is about 600000 t,but currently the development and utilization of pomegranate resources is relatively.The fermentation of fruit and vegetable is the effective measure to maintain or improve quality and extend the shelf life.It can not noly improve the utilization rate of resources and also enrich product variety to develop new fermented pomegranate drink.In this study,compared the effects of different lactic acid bacteria fermentation on the quality of fermented pomegranate juices（FPJs）,and the antioxdiant compounds and volatile compounds of FPJs as affected by high hydrostatic pressure（HHP）and thermal processing（TP）were studied,so as to optimize the process of FPJs.The main conclusions of the study are as follows:1.Compared the effects of four different lactic acid bacteria（LAB）on the quality of FPJs during fermentation,and the principal component analysis（PCA）was adopted to analyze various indicators.The results indicated that contents of total phenol,ascorbic acid,anthocyanin and DPPH free radical scavenging rates of FPJs compounded with Lactobacillus plantarum and Lactobacillus acidophilus decreased by 7.2%（75.9 mg/100 mL）,37.7%（0.066mg/mL）,34.5%（42.38 mg/L）and 21.6%,repectively.While decreased by 23.0%,58.5%,51.22%and 45.92%in naturally fermented samples.2.Through sensory evaluation combined with response surface experiment,it is determined that the optimal process for the preparation of FPJs as follows:the added amount of sugar solution is 12%,the inoculation amount of Lactobacillus plantarum and Lactobacillus acidophilus is 1.5%（the cell concentrations is 1.23×107 CFU/mL）,the fermentation temperature is 28℃,and the fermentation time is 48 h.The FPJs are brick red with no precipitation,suitable for sweet and sour and comfortable in taste.The contents of total phenol,anthocyanin and the DPPH radical scavenging activity were 803.34±13.04mg/L,41.30±1.11mg/L and 225.29±4.74μM Trolox/L,respectively.3.Volatile compounds of FPJs were measured by GC-MS technology.Total 38 volatile flavor compounds were present in FPJs.Compared with the unfermented pomegranate juice,the levels of esters（42.59%）and alcohols（35.75%）displayed the most significant increase in FPJs.The alcohols primarily included 1-Butanol（6.21%）,Phenylethyl Alcohol（5.95%）,2-Heptanol（5.84%）,2-Nonanol（6.11%）,and the esters mainly composed by Ethyl Acetate（21.97%）,Ethyl butyrate（4.54%）and others ethyl esters compounds.In addition,ketones and acids were detected,which harmonized to form the special flavor of FPJs.4.Examined the inactivation of microorganisms and the HHP kinetic model in FPJs at different conditions（400 MPa600 MPa,3min10min）.The results showed that the inactivation curves of the microorganisms of HHP were conforms to the Weibull model,the total color difference（ΔE）values,total soluble solids（TSS）,pH and titratable acidity（TA）had not significantly（p>0.05）changed during the processing.For total flavonoids,total phenols,anthocyanins,and antioxidant activity,the maximal retention of 91.18%（797.90±3.93 mg/L）,97.52%（783.41±2.87 mg/L）,95.69%（39.52±0.75mg/L）,and 95.89%（216.03±4.61μM Trolox/L）was achieved at 600 MPa/3 min,which was 4.62%,24.61%,26.83%,and 7.08%higher than that in the thermal processing（TP,65℃/20 min）treated ample.5.The storage characteristics and quality changes of FPJs of FPJs treated by HHP（500MPa/10 min）and TP during storage at 4℃ and 25℃ were investigated.The results showed that the Aerobic plate count（APC）of FPJs treated by HHP and TP was less than 2 log during storage of 30 days,and the Yeasts and molds（Y&M）were not detected during storage,which met the requirements of the national standard（GB 7101-2015 and NY/T 434-2016）,indicated that the HHP and TP could guarantee the microbial safety of FPJs.The pH,TSS,and TA in FPJs were relatively stable and did not change significantly（p>0.05）during storage,while the content of antioxidant components such as total phenols,flavonoids and anthocyanins were decreased with the extension of storage time.The DPPH free radical scavenging capacity and O2-scavenging capacity in FPJs were significantly and positively correlated with the contents of flavonoids,total phenols and anthocyanins content,and the correlation coefficients ranging from 0.958 to 0.995.With the extension of storage time,the content of esters and alcohols in FPJs were decreased.Comprehensive analysis found that FPJs treated with HHP could better maintain their quality when stored at 4℃. |
