Analysis Of Oxidation And Evaluation Indexes Of Instant Cereal Flours During Storage

Instant cereal flour is a kind of product which contains one or more cereals and is cooked by different processing methods.It can be eaten directly or by mixed with hot water.In recent years,different kinds of instant cereal flours are very popular because of rich nutrition and convenience.However,most of the evaluation criteria are based on the enterprise standards and mainly focus on the nutritional and microbial indexes.There is no standarded index which could evaluate the oxidative deterioration of instant cereal flour.Therefore,this paper was devoted to solving these problems and the main contents were as follows:The effects of different processing methods(extrusion and drum drying)on the oxidation stability of the instant cereal flours(oat and millet)during the accelerated storage(50?)were investigated.During the accelerated storage,these oxidation indexes(fatty acid value,peroxide value,MDA value,fat content and fatty acid content)of the two instant cereal flours by extrusion and drum drying were similar.As the storage time increased,the fatty acid value and MDA value both increased,the fat content decreased,the relative content of saturated fatty acid(SFA)increased and the relative content of unsaturated fatty acid(UFA)decreased.The changes of fatty acid composition had a good correlation with the peroxide value and MDA value.Specially,the peroxide value of instant millet flour increased while that of the instant oat flour firstly increased and then decreased with the storage time increasing.During the accelerated storage(50?),the oxidation stability of the four kinds of instant cereal flours(oat,millet,black rice and brown rice)which were all prepared by extrution was analyzed.The results showed that the values of fatty acids and MDA value of the instant black rice and brown rice flours showed an increasing trend;the peroxide value of the instant black rice flour firstly increased,then gradually decreased,and finally increased while the instant brown rice flour increased.The oxidation rate and the values of the oxidation indexes(especially the fatty acid value and peroxide value)were significantly different due to the differences in fat content and fatty acid composition of the four cereals.Based on the changes of the oxidation indexes during accelerated storage,the MDA value was used as the main index to evaluate the degree of oxidation of the instant cereal flours.Storage of instant cereal flours finished when MDA value reached 0.2 ?g/g.The effects of normal packing,vacuum packing and antioxidant(L-ascorbyl palmitate)addition on the fatty acid value,peroxide value,MDA value and fat content of the instant millet and oat flours during the accelerated storage(50?)were compared.For normal packing,vacuum packing and antioxidant(L-ascorbyl palmitate)addition,the fatty acid value,peroxide value and MDA value of the instant millet flour all increased and could be fitted by first-order kinetics equation.The fatty acid value and MDA value of the instant oat flour increased and could also be fitted by first-order kinetics equation.Compared with normal packing,the storage time of the instant millet flour by vacuum packaging was delayed for 7 d while that of the instant millet flour by antioxidant treatment was delayed for 5 d.The storage time of the instant oat flour by vacuum packaging was delayed for 20 d while that of the instant oat flour by antioxidant treatment was delayed for 10 d.Accroading to the relationship between temperature and shelf life coefficient of fat,during the storage at 20?,compared with normal packing,the shelf life of the instant millet flour by vacuum packaging could be delayed for 56 d while that of the instant millet by antioxidant treatment could be delayed for 45 d.The shelf life of the instant oat flour by vacuum packaging could be delayed for 162 d while that of the instant oat flour by antioxidant treatment could be delayed for 78 d.In conclusion,the storage effect of vacuum packing is optimal among normal packing,vacuum packing and L-ascorbyl palmitate treatment.