| Prunus persica is also called peach,belongs to the Rosaceae family,which can be variously classified by shape(elongated/round or flat),flesh colour(yellow or white),or fuzzless skin(the nectarine group),etc.Yellow-fleshed peaches are known have a lot of nutrients inside such as vitamin,carotenoids,phenolics,dietary fibers,trace elements and other bioactive substances.The common various types of yellow-fleshed peach products are fresh,canned and dried fruits;moreover,yellow-fleshed peach crisps is a new peach dried product and begin to be developed as a new fruit snack.Technological drying processes have an important role in the final yellow-fleshed peach crisps quality and especially to the antioxidant activity..Every drying technology has its own advantages and disadvantage;furthermore,explosion puffing drying(EPD)become very a promising technology for higher efficiency since it enhanced the overall quality of dried fruit products.However,further research is still needed to optimize the using of EDP on the yellow-fleshed peach crisps to get the maximum nutrition content.It is very important to find the suitable EPD methods for preserving the overall quality.This research mainly focuses on the EPD characteristic of different variety of yellow-fleshed peach;also compare the effect of drying on the yellow-fleshed peach quality between EPD and other drying methods;Optimization of EPD processes for high-nutritional value on the yellow-fleshed peach crisps;and the effect of storage condition on the carotenoids stability of yellow-fleshed peach crisps.The results obtained are as follows:1.The characteristics of seven cultivars of yellow-fleshed peach crisps dried by EPD showed the crispy appealing(3.48-5.13 N)and attractive colour.The nutrition content such as total carotenoids(25.89-43.55 ?g/g d.w),vitamin C(92.59-140.21 mg GAE/g d.w),total phenolics acid(6.69-6.76 mg GAE/g d.w),and the antioxidant activity value(DPPH,FRAP,and ABTS)for all yellow-fleshed peach crisps cultivars were measured.To choose the best cultivars,the Principal Component Analysis(PCA)and System Cluster Analysis(SCA)has been used.PCA conducted to distinguish the indicators among cultivars and suggested four principal components that the most important factors affecting the yellow-fleshed peach crisps quality.The four PCs through PCA,are ?-carotene,phenolics,zeaxanthin and FRAP for PC1,PC2,PC3,and PC4,respectively.According to the PCA results,the SCA is used to classify the different cultivars with the same characteristic and divided into four main groups on the basis of the measured quality evaluation indicators.The final result showed Jinhui cultivars was chosen due to the high score of PCA and SCA link distance.2.The yellow-fleshed peach Jinhui cultivar was used to compare the explosion puffing drying(EPD)with other drying methods(vacuum freezing drying(VFD),hot air drying(HAD),and vacuum microwave drying(VMD)),in order to evaluate the suitable methods for yellow-fleshed peach crisps production.VFD dried fruit crisps obtained a low hardness and a high number of a peak(hardness:10.21±0.13 N and crispness:6.15±0.06 N),while the microstructure was loosened in EPD samples that provide crispness and hardness.VFD and EPD preserve the quality of carotenoids,vitamin C,and DPPH antioxidant capacity value.VMD and HAD led to higher retentions of colour,total phenolics,and ABTS·+?radical scavenging capacity.Base on the principal component analysis of present investigation,we conclude that VFD can better preserve active component but lack of texture evaluation for yellow-fleshed peach crisps.Furthermore,compared with other drying methods,the EPD could produce a good impact on texture properties and also can maintain the overall quality and antioxidant activity.3.Response surface methodology(RSM)was used to comprehensively evaluate the pilot scale non-fried explosion puffing drying(EPD)conditions for developing high-value yellow-fleshed peach crisps.The independent variables were different levels of vacuum drying temperature,vacuum drying time and puffing pressure difference.The responses were crispness,total colour difference(?E),total carotenoid content(TC)and DPPH(ascorbic acid equivalent antioxidant capacity(AEAC))value.Statistical analysis revealed that vacuum drying temperature significantly affected all the responses,puffing pressure difference showed maximum influences on TC,AEAC and crispness,while vacuum drying time showed influences on TC and AEAC.The optimum EPD conditions obtained by RSM were vacuum drying temperature,vacuum drying time and puffing pressure difference of 73 ?,144 min and 0.05 MPa,respectively.At this optimal condition,crispness,AE,TC,and AEAC value were found to be 7.3 N,18.3,53.5 ?g/g d.w.and 865.4 mg AA/100g,respectively.The EPD-dried yellow-fleshed peach crisps contained higher amounts of carotenoids and AEAC values when compared to hot-air dried samples,they were also found to be crispier than vacuum freeze-dried samples.4.The sugar crystallization and the rate of carotenoid degradation as a function of aw in explosion puffing-dried yellow-fleshed peach crisps stored at various levels of relative vapor pressure(RVP)(11.3-84.3%)have been studied.The loss of absorbed water was well correlated with the crystallization of an amorphous sugar matrix at corresponding RVP greater than or equal to 57.6%.The X-ray diffraction(XRD)pattern and scanning electron microscopy(SEM)analysis were confirmed the crystalline phenomenon of sugar crystallization.The carotenoid stability increased as the RVP level increased,up to 57.6%and sharply increased in carotenoid degradation at RVP 75.3-84.3%.The carotenoid contents decreased over time by following pseudo-first-order kinetics during storage due to sugar crystallization.The colour measurement parameter(L*?a*and b*)values decrease significantly when the storage condition at higher RVP as same as degradation carotenoids occurred.The water activity and sugar crystallization affected the stability of carotenoids in explosion puffing-dried yellow-fleshed peach crisps. |
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