Changes And Control Of Maillard Reaction Extent And Related Quality In Drying Process Of Jujube Powder

Jujube is peculiar to our country, rich in nutrition, and has unique health value. Jujube processed into flour, which reduce the moisture content, transportation costs, extend shelf life, storage period, and is convenient to consumption and preservation, improve value-added products. Jujube powder thermal processing prone to take place Maillard reaction, which affect the products color and aroma resulting in unstable product quality, the influence of drying methods on the extent of Maillard reaction and associated quality need to be studied in-depth, which is the basis of improving the quality of jujube powder and production technology level. Date syrup as the raw material, this paper studied the effect of drying methods on the Maillard reaction and the degree of browning, aroma components, functional characteristics of jujube powder firstly, the impact of vacuum microwave-hot air combined drying conditions and chemical composition in date syrup on the Maillard reaction and the degree of browning, aroma components, functional characteristics of jujube powder secondly, and optimized the conditions of vacuum microwave-hot air combined drying produced high-quality jujube powder. The main results and conclusions were as follows: 1. Effect of drying methods on extent of Maillard reaction and quality of jujube powderJujube pulp as raw material, four kinds of drying methods including hot air drying, drum drying, spray drying and vacuum microwave-hot air combined drying were used to obtain jujube powder, then we compared the degree of browning, color values, furosine, 5-HMF, reducing sugars, amino nitrogen contents, aroma components and antioxidant capacity of jujube powder. The results were as follows, Maillard reaction of hot air drying dried jujube powder was severe, jujube powder color was red and yellow, with the most aromatic components species; the contents of aroma components in drum drying dried jujube powder was lowest; Maillard reaction degree of spray drying dried jujube powder was minimum, jujube powder color was lightest and partial white, aroma contents was most with low molecular weight acids, alcohols based; vacuum microwave-hot air combined drying dried jujube powder had a high degree Maillard reaction in which organic acids was the lowest; hot air drying and vacuum microwave-hot air combined drying dried jujube powder had higher reducing power, DPPH radical scavenging ration and total polyphenols contents. Correlation analysis showed that the drying methods affected the Maillard reaction degree and not only the browning degree and color, but also the antioxidant activity and flavonoids contents of jujube powder further. Acuum microwave-hot air combined drying process had the shortest time and highest efficiency, the comprehensive evaluation of color, aroma and antioxidant capacity was highest of jujube powder, and we choosed the acuum microwave-hot air combined drying as suitable drying method for jujube powder at last. 2. Effect of microwave power and vacuum degree on extent of Maillard reaction and quality of vacuum microwave-hot air combined drying dried jujube powderJujube pulp as raw material, we used vacuum microwave-hot air combined drying to obtain jujube powder and studied the effect of microwave power and vacuum degree on the extent of Maillard reaction and quality of jujube powder. The results were as follows, Maillard reaction degree in jujube powder was increased first and then decreased with the microwave power increased, while the type and contents of aroma components in jujube powder showed a downward trend; with vacuum degree increased, Maillard reaction degree in jujube powder showed a downward trend, with browning degree, antioxidant capacity decreased, vacuum degree had little effect on aroma species, and a significant influence on the aroma ingredients contents. 3. Effect of chemical composition in date syrup on extent of Maillard reaction and quality of vacuum microwave-hot air combined drying dried jujube powderJujube pulp as raw material, we used vacuum microwave-hot air combined drying to obtain jujube powder and studied the effect of the amount of starch, moisture, reducing sugars, amino nitrogen contents, and p H on the extent of Maillard reaction and quality of jujube powder. The results were as follows, increasing the amount of starch in raw materials, browning degree, furosine, flavonoids contents, antioxidant activity of jujube powder showed a downward trend overall; with water content increased in jujube paste, Maillard reaction degree was decreased and degree of browning, total acid, flavonoids contents, antioxidant activity were decreased; with amino nitrogen content, the p H increased in date syrup, the extent of Maillard reaction of jujube powder was increased, and browning degree and color deepened. 4. Optimization of production process of jujube powder by vacuum microwave-hot air combined drying7-factors and three levels orthogonal experiments results showed that under conditions of the microwave power 440 W, vacuum degree-35 kp, starch added in an amount of 10%, moisture content of 80%, reducing sugar content of 10 g/100 g, amino nitrogen content of 48 mg/100 g, jujube pulp p H 7, moderate degree of Maillard reaction occurred in jujube powder, whose aroma rich, color close to the color of jujube, flavonoids, polyphenol content high and antioxidant capacity strong.