Study On Antioxidant And Color Stability Of Dehydrated Semi - Dry Apple

Fruits and vegetables are rich in a variety of antioxidants, these antioxidants can scavenge free radicals, anti ageing, anti allergy, improve immunity and other function. Using apples as raw materials, this paper discuss changes of oxidation resistance and color stability about dehydrated semi dried apple slices in the different water activity. Analysis the influence, which about oxidation resistance and the color stability, of semi dried apple slice in different water activity lowering agent on the dehydration. To investigate the mechanism of dehydration of semi dried apple slices about non enzymatic browning, and puts forward the method of controlling non enzymatic browning of the dehydration of semi dry apple slices.In 20 ℃ after 30days, total phenolic, total flavonoid, ascorbic acid, DPPH-scavenging rate of apple slice of semi dried dehydration in the different water activity had all decreased. The degree of Browning about them had a rising tendency. The loss rate of total phenolic from big to small:Aw0.701> Aw0.668> Aw0.605>Aw0.562. The loss rate of total flavonoid from big to small:Aw0.701> Aw0.668> Aw0.605> Aw0.562. The loss rate of ascorbic acid from big to small:Aw0.562> Aw0.605> Aw0.668> Aw0.701. The loss rate of DPPH-scavenging rate from big to small:Aw0.701> Aw0.668> Aw0.605> Aw0.562. The rise of the degree of browning from big to small:Aw0.701>Aw0.668>Aw0.605>Aw0.562.The result of sensory evaluation show that:browning degree of Aw0.605 dehydration semi dried apple slices is smaller; color stability of it is steadier; and excellent taste of it is nicer. Aw0.605 are the best water activity of dehydration semi dried apple slices. Combined antioxidant index with sensory evaluation are relatively optimal, Aw0.605 is suitable for dehydration semi dried apple slices in storage, including water 24.60%.The experiment of storage shows that:blanching and low temperature are fit to retention of apple slices in total phenolic, flavonoid, ascorbic acid, DPPH-scavenging rate, slow down the browning.Using different water activity lowering agent on osmotic dehydration of apple, with the hot air drying, to get semi dried apple slice in Aw0.605. The results show that:compared with the fresh apple, total phenolic of apple slices in trehalose +NaCl dried group content the lowest loss. Total phenolic of apple slices in high fructose corn syrup dried group followed by it, the loss rate is 46.96%. Total flavonoid of apple slices in trehalose +NaCl dried group content the lowest loss, the loss rate of total flavonoid in apple slices in high fructose corn syrup dried group is 27.15%. Ascorbic acid of apple slices in no infiltration group content the lowest loss, the loss rate of ascorbic acid in apple slices in high fructose corn syrup dried group is 17.43%. DPPH-scavenging rate of apple slices in trehalose+NaCl dried group content the lowest loss. DPPH-scavenging rate of apple slices in high fructose corn syrup dried group followed by it, the loss rate is 2.39%. The degree of browning about apple slices in trehalose +NaCl dried group content the lowest loss, the degree of browning of apple slices in high fructose corn syrup dried group followed by it, with the initial degree of browning increased by 0.11.In 20 ℃ after 30days, total phenolic of apple slices in high fructose corn syrup dried group content the lowest loss, the loss rate is 24.22%.Total flavonoid of apple slices in high fructose corn syrup dried group content the lowest loss, the loss rate is 24.87%. Ascorbic acid of apple slices in trehalose dried group content loss the lowest, the loss rate of apple slices in high fructose corn syrup dried group is 68.41%. DPPH-scavenging rate of apple slices in trehalose +NaCl dried group content loss the lowest. DPPH-scavenging rate of apple slices in high fructose corn syrup dried group followed by it, the loss rate is 33.19%. The degree of browning about apple slices in trehalose dried group content loss the lowest, the degree of browning of apple slices in high fructose corn syrup dried group with the initial degree of browning increased by 0.76. The result of sensory evaluation show that:high fructose corn syrup as apple slices of water activity lowering agent, apple slices taste the best, but the color stability. High fructose corn syrup as apple slices of water activity lowering agent, antioxidant index and sensory evaluation are relatively optimal.After 30 days, the index, content of chlorogenic、epicatechin、quercetin、phloridzn、 catecbin、rutin、5-HMF, was measured by HPLC. Analysis change of the ascorbic acid, total phenols, amino nitrogen, reducing sugar and total sugar, to investigate the mechanism of dehydration of semi dried apple slices about non enzymatic browning. The results show that: oxidative condensation of degradation of ascorbic acid and polyphenol is the main factors about non enzymatic browning of Aw0.605 apple slices. Maillard reaction is not the main factors about non enzymatic browning of Aw0.605 apple slices.In 20 ℃ after 30days, color change of apple slices with using high fructose corn syrup+ CaCl2 and high fructose corn syrup+NaiSO3 on osmotic dehydration from big to small:no infiltration group> high fructose corn syrup+Na2SO3> high fructose corn syrup+CaCl2. The rise of the degree of browning about apple slices from big to small:no infiltration group> high fructose corn syrup+Na2SO3> high fructose corn syrup+CaCl2. Compared with change of color and the degree of browning,we can know that in storge color stability about apple slices in high fructose corn syrup+CaCl2 group is better than in high fructose corn syrup+Na2SCl2 group. High fructose corn syrup+CaCl2 group, which slow down the occurrence of non enzymatic browning, is better for propecting total phenolic and ascorbic acid of dehydrated semi dried apple slices.