| With the improvement of the consumption level and the health awareness,people pay more and more attention to chip snack foods with healthier ingredients such as fruit and vegetable.This paper focus on the product of apple chips,not only because apple is the ingredient with comprehensive nutritional components and extremely high production,but also because apple chips could satisfy the need of good taste,health consideration and maximum profits of manufacturing.Best quality of apple chips with optimal processing parameter were achieved by extruding them with microwave puffing,which was a more effective and safer method.In this paper,pre-drying time,microwave power and microwave time were optimized by sensory evaluation score and yield using response surface method to obtain the good quality chips.This paper could also be a strong support for apple production industry through analyzing the changes of nutritional components of apple chips during processing.The main outcome was shown below:(1)With the increase of the pre-drying time,the brittleness approaches to 1s after 600 min,hardness and chromatic aberration first increased to 1000.67g and 25.24 and then decreased,sugar and acid ratio increased to 24.23;Microwave power and time have similar effects on product quality.With the increase of the power,the brittleness and the ratio of sugar to sour continue to decrease to 0.7s and 18,hardness reach the maximum value of 1060.33g at 600w and then decreased,the chromatic aberration is increasing to 49.98;With the microwave time increases,the hardness first increased and then decreased,reach the maximum value of 1066.67g at 30s,brittleness reduced to 0.71 s,sugar and acid ratio decreased to 18.32,the chromatic aberration increased to 30.91.(2)The a*,brittleness and chromatic aberration were negatively correlated with the sensory evaluation score of apple crisp.The ratio of sugar to acid,hardness,L*and b*were positively correlated with the sensory evaluation score of apple crisp,And the sensory evaluation score has the strong correlation with L*,sugar,acid ratio and chromatic aberration.We believe that the sensory evaluation score can accurately characterize the quality of apple chips(3)Single factor experiments to determine the best product quality when the pre-drying time between 60-100min,microwave power between 600-1000w,microwave time between 20-40s.Advanced optimization,pre-drying time,microwave power and microwave time were 89.09min,729w and 28,89s,respectively,when the best quality of the apple chip.At this point the apple crisp sensory quality score is 94.18,the yield is 0.9016.The fit of the verification experiment,is good.(4)The pre-drying process had no significant effect on the extraction rate,weight-average molecular mass,galacturonic acid and degree of esterification of pectin.But when acetylated,the pyran ring conformation may change.The pectin extraction rate increased 16.47%(P<0.01),weight-average molecular mass became large,no change in galacturonic acid content and degree of esterification increased after puffing.By the analysis of FT-IR spectroscopy,Microwave has a certain impact on the C-H bond and carboxylate ester bond on the galacturonic acid methoxy of the pectin.Solution viscosity becomes smaller,the solubility increases.(P<0.05)(5)The loss of nutrients occured mainly in the pre-drying process.A large amount of water evaporated from the apple slices causes the loss of soluble sugar and organic acids,the ratio of sugar to acid reduced.And the thermal effects the AA oxidized and total VC content decreased.Although the flavonoid compounds are structurally damaged,but microwave treatment makes intermolecular squeezing and crashing,Leading to cell membrane broken,flavonoid compounds were dissolving pulped and the extraction rate increased slightly. |
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