Dielectric Properties Of Black Bean And The Impact Of Radio Frequency Heating On Qualities Of Black Bean

Black bean is rich in nutrients(protein,fat,cellulose,a variety of vitamins and trace elements),also contains antinutritional factors such as phytic acid,tannin,saponin,and trypsin inhibitor.These antinutritional factors can hinder the absorption and utilization of nutrients,and excessive intake will cause harm to human health.Searching for a nice processing method feasible to reduce antinutritional factors and maximally maintain the nutrient quality of black beans is important for the application of black bean products.Dielectric heating can heat materials without any conduction process,with a fast heating rate and short heating time,and maintain the nutrition composition of the processed products well.In addition,the instantaneous high temperature dielectric treatment can also preferentially eliminate exogenous living pollutants in food,improve food storage quality,and prolong the shelf life of the product.In this paper,black bean was chosen as the research object,the effects of frequency,temperature and water content on the dielectric properties were studied using coaxial probe,in order to deeply understand the control factors of dielectric heating.The results indicated that the dielectric constant and loss factor of the bean samples decreased as the frequency increased,especially at higher water content and temperature.Dielectric constant and loss factor increased as temperature and moisture content increased.Power penetration depth decreased when the moisture content,temperature and frequency decreased.The influences radio frequency heating on nutritional composition,physicochemical properties,microstructure and removal of anti-nutritional factors in black bean were studied.The results showed that the treatment caused the loss of nutrients.The content of fat and total amino acids decreased significantly while a less loss in crude protein.As for anti-nutritional factors,treatment significantly reduced the contents of saponin,phytic acid and tannin,and decreased the activities of trypsin inhibitor.Radio frequency heating initiates changes of subunit structures in black bean protein,and promoted protein agglomeration as well.The results of the study showed that radio frequency processing had little impact on nutritional components and storage protein structures of black bean due to its mild processing conditions.However,it effectively eliminated the anti-nutritional factors as well.Thus,radio frequency processing possessed a good application prospect in thermal processing of legume products.