| In this paper,Xizhou Mi 17,Xinjiang,was used as experimental material,hot air drying and vacuum freeze-drying hami melon slices were prepared by using the composite protecting liquid,the process conditions of hot air drying and vacuum freeze drying were optimized by using the method of fuzzy mathematics and response surface.The microstructure and aroma components of the products prepared by the two drying methods were compared and analyzed.In order to maintain the quality of dried Hami Melon during shelf life,the changes of basic physical and chemical indexes of two kinds of dried Hami Melon during storage were determined,and the optimum packaging storage mode was determined by comprehensive analysis.The specific results are as follows:(1)The effects of citric acid,sodium chloride and calcium chloride on sensory evaluation of Hami melon slices were investigated by single factor experiments.The response surface color protection process was optimized by using fuzzy mathematics and Box-Behnken design.The optimum processing conditions of compound color protection solution were as follows:0.44%citric acid,0.26%calcium chloride and 0.15%sodium chloride.Under these conditions,the theoretical value of sensory evaluation of dry color protection effect of Hami melon was 91.28 points,and the result of response surface design was accurate and reliable.The model can be used to analyze and predict the treatment of color-protecting liquid in the drying process of Hami melon slices.The Total sugar content,Vc content,Phenol content,Flavonoid content,Hardness,L value and b value of hot-air dried Hami melon tablets were 19.92%,15.69 mg/100g,268.16 mg/kg,9.05 mg/g,0.46 kg/cm2,77.83 and 36.70 respectively.Hami melon dried golden,sweet and sour,melon fragrance,there is a certain degree of chewing power.(2)The optimum conditions of vacuum freeze-drying process for Hami melon slices were analyzed and obtained by means of fuzzy mathematics combined with response surface optimization test.The optimum conditions were as follows:pre-freezing time was 3.2 h,material thickness was 9 mm,drying time was 24.2 h.Under these conditions,the sensory evaluation of Hami melon dried was 89.96 points by three parallel verification tests,which basically coincided with the predicted value,and the reliability of the model was confirmed.The regression model fitted the experiment well,which showed that the results obtained by response surface design were accurate and reliable.The total sugar content in dried Hami melon was 20.12%,the Vc content was 12.10 mg/100g,the total phenol content was 282.22 mg/kg,the total flavone content was 12.35 mg/g,the hardness was 0.33 kg/cm2,the L value was 81.59,and the b value was 18.21.Better to maintain the original color,smooth surface,with stomata,uniform texture,crisp taste,melon aroma.(3)Microstructure of two kinds of dried Hami melon slices was observed by scanning electron microscopy.The surface of hot-air dried Hami melon slices was smooth without holes,cells folded and the whole structure collapsed.Vacuum freeze-dried Hami melon slices were porous and loose without disintegration,folding and atrophy,and a small number of holes were distributed.GC-MS detected 30 volatile components from hot air drying and vacuum freeze drying of dried Hami melon.The main aroma components of hot air dried Hami melon slices are esters,alkanes,ketones,aldehydes,alcohols,aldehydes and carboxylic acids.The highest content of geranyl acetone in ketones is 19.47%,which makes the products have sweet rose aroma.The main aroma components of vacuum freeze-drying Hami melon slices are alcohols,esters,alkanes,ketones,aldehydes and ethers.The highest content of β-ionone in ketones is 26.12%,which makes the products have flower and fruit aroma.Different drying treatments had significant effects on the microstructure and aroma components of Hami melon slices.(4)The results of different packaging methods and light conditions showed that the loss rate of dark storage quality indicators was significantly lower than that of light storage,and the loss rate of quality indicators of vacuum packaging was significantly lower than that of atmospheric packaging.The change of browning degree,total phenol content and total flavone content of dried Hami melon could be effectively reduced by vacuum and dark storage,and the shelf life of fresh-keeping could be delayed.It can keep the quality of dried Hami melon better.After 150 days storage,the browning degree,Vc content,total sugar content,total phenol content and total flavonoids content of dried Hami melon were better than those of normal pressure storage,which were 0.12 OD420/g,7.40 mg/100g,19.61%,193.26 mg/kg and 5.42 mg/g.In vacuum freeze-drying,the browning degree,VC content,total sugar content,total phenol content and total flavonoids content of dried Hami melon were maintained well,which were 0.07 OD420/g,6.48 mg/100g,19.00%,198.66 mg/kg and 6.76 mg/g,followed by atmospheric pressure light-shielding storage. |
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