| As a kind of natural health food,okras were rich in polysaccharides,vitamins,carotenoids,microelements and other nutrients.However,the okra pods had a high moisture content and were sensitive to temperature.After being picked and placed in normal temperature for a few days,they would suffer from water loss,softening,fibrosis,mildew and other deterioration of quality,and produced about 15%processing by-products,resulting in resource waste and environmental pollution.There were still nutritive substance,active component and utilization value in some of the okra processing by-products.Therefore,it was urgent to explore reasonable and effective methods for the comprehensive utilization of okra by-products.On the basis of previous studies,the researches on okra by-products drying process,drying model and edible film preparation of okra by-products powders were carried out in this project,and the following progresses were made:1.The effects of different cutting types and drying methods on drying characteristics,physicochemical properties and antioxidant capacity of okra were examined experimentally.As expected,the drying time decreased with increased drying temperature,and VC samples had shorter drying time than that of HC samples both HA and HP.The overall quality of dried okra samples depended on cutting types and drying methods.HP samples had higher Vc retention and antioxidant activity compared with HA.This study indicated that HP was a promising drying method for okra quality preservation,especially at VC-HP-50?,as it allowed better reservation of chemical compositions to obtain higher comprehensive score.Through comprehensive analysis,the best drying process of okra was VC-HP-50?.The findings in current work could provide necessary information and theoretical foundation for okra drying industrially.2.After fitting,analyzing and comparing seven models of okra by-products thin layer drying,it was concluded that Weibull model had the best fitting degree with the data of okra hot-air drying and heat pump drying,which was the most suitable for describing okra drying process,followed by Page model.The regression analysis of the Weibull model parameters"?"and"?"with the drying temperature of okra hot air drying and heat pump drying was carried out,which was conducive to the transformation of the empirical model into an operable method to describe,analyze,optimize and predict the process of okra hot air thin layer drying and heat pump thin layer drying.The Deffff determined by Weibull distribution model ranged from 0.992×10-99 m2/s to 4.409×10-99 m2/s for HA and 1.915×10-99 m2/s to 5.291×10-99 m2/s for HP.The Ea was 37.00,and 35.91 kJ/mol for the samples dried by HC-HA and VC-HA,29.25,and21.40 kJ/mol for HC-HP and VC-HP,respectively.3.In order to make comprehensive use of okra by-product raw materials and study the edible film with good properties,the normalized comprehensive scoring method was adopted to optimize the formula of okra by-product powder edible film.The results revealed that edible films composed of 2.0%okra by-product powder,7.0%potato starch and 0.3%sodium alginate showed the composite scores of 0.80.Whose water vapor permeability rate was172.61±3.53 g·m/m2·d,tensile strength was 2.45±0.05 MPa,elongation at break was 35.58±2.59%,transmittance was 18.82±0.52,solubility was 25.58±1.15%.The results of fourier transform infrared spectrum and scanning electron microscope showed preferable compatibility between film okra by-product powder and potato starch.This study can provide references for the comprehensive utilization of okra by-products and the production and application of edible film. |
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