Process Optimization And Quality Study Of Vacuum Low-temperature Fried Crispy Dates

Xinjiang has a unique climate and light conditions,and under the superior growing conditions,grey dates are round and full,with small nuclei,thin skin,firm and delicate flesh,sweet and juicy,and rich in nutrients,suitable for fresh eating and processing.Fresh dates have a short shelf life,and most of the current processed products are at the primary stage of rough processing,with a single level of processing,low added value and serious nutritional loss.Dried jujube is dried and directly marketed as a speciality,snack or beauty care product,with a low market share in further processing,which does not meet the market demand for high quality jujube products.In this experiment,fresh and dried grey dates were used as the raw material for the test,and the prediction of the shelf life of vacuum low-temperature deep-fried crispy dates was studied.The experimental results were as follows.(1)For the vacuum low-temperature frying process of crisp-ripened,full-red-stage fresh dates,the process parameters conditions were screened by four single-factor tests of frying time,frying temperature,vacuum and de-oiling time,and the process conditions of vacuum low-temperature frying crisp dates were optimised by response surface tests based on the single-factor tests with oil content and sensory scores as the investigative indicators.The optimal process conditions for deep-frying crispy dates were 40 min frying time,115℃frying temperature,0.08 MPa vacuum and 4 min de-oiling time.and good organoleptic quality.(2)The vacuum low-temperature frying process with dried dates as raw material was firstly carried out to investigate the effects of rehydration time,rehydration temperature and material-liquid ratio on the rehydration quality of dried dates,using total sugar,soluble solids content and hardness as indicators.The moisture content of the rehydrated dates was 43.02%under these conditions.The rehydrated dates were frozen and then subjected to vacuum low temperature frying process.The process parameters were selected by four single-factor tests:frying time,frying temperature,vacuum degree and degreasing time,and the process conditions for vacuum low-temperature frying of crispy dates were optimised by response surface tests based on the single-factor tests with oil content and sensory scores as indicators.The optimum frying process was 30 min,frying temperature 100℃,vacuum 0.08 MPa and de-oiling time 5 min,under which the oil content of the fried product was 16.56%and the sensory score was 88.9.The optimized process resulted in a lower oil content and higher sensory score.(3)The shelf life of the fried dates was investigated and the storage life of the fried dates was predicted using the acid value and peroxide value of the oils and fats as indicators.The acid value and peroxide value of fried dates were studied at storage temperatures of 25℃,35℃and 45℃under different packaging conditions and storage times.On the basis of this,a first-order kinetic model of fatty acid defeat combined with the Arrhenius formula was developed to predict the shelf life of fried crispy dates with R~2>0.9,and the model fit was good.The model provides data support for the development of jujube processing and leisure food,alleviates the sales pressure of fresh jujube marketed centrally,realizes the extension of fresh jujube processing industry and provides data support for vacuum low temperature fried jujube products.