Study On Processing Technology Of Canned Guanxi Pomelo

Guanxi pomelo is a kind of nutrient-rich fruit. It tastes sweet with slightly sour and has a special medical value and health care fuction. Presently, Guanxi pomelo deeply processed products in the market are various, including grapefruit juice, grapefruit tea, candied grapefruit and so on. In order to further enhance the value of Guanxi pomelo, the company fied a processing requirement of canned Guanxi pomelo. There are a lot of processing difficulties, such as its difficulty of removing cyst membrane, its bitterness after processing and its browning during storage. Therefore, this research studied the processing technology of canned Guanxi pomelo, produced canned Guanxi pomelo and developed quality standard of the product. The main conclusions are as follows:The technology of removing cyst membrance was studied. The method of removing cyst membrance by alkaline was choosed after comparing alkaline and enzymatic methods. The effects of alkali concentration, temperature and additives were compared. The procession of removing cyst membrance was determined: alkaline solution 1%, temperature 40℃and stirring time 4~5 min. The optimal rinsing method was three grade counter-current rinsing with 15, 10 and 5 min respectively, finally rinsed 5 min by 1% citric acid, with a average water consumption of 1.8~2 liters per kilogram pulp.The effects of different methods of debittering on Guanxi pomelo were studied. The effects ofβ-cyclodextrin andβ-glucosidase enzyme on debittering were compared. As forβ-cyclodextrin, the remaining content of naringin was 91.6% and that of limonin was 35.9% under the best conditon of 40℃, 10 min and 0.6%β-cyclodextrin.β-cyclodextrin made a weak action of naringin, therefore it was added to the sugar to achieve the purpose of debittering instead of soaking pulp in it. As forβ-glucosidase enzyme, the remaining content of naringin was 78.5% and that of limonin was 45.5% under the best conditon of 40℃, 50 min and 0.7 mL/Lβ-glucosidase enzyme.β-glucosidase enzyme performed a faint effect of removing naringin and limonin, and because of its high cost, so the method was not adopted in the actual production.The browning reason was investigated. It was mainly due to non-enzymetic browning but not enzymetic browning. The effects of different concentrations of sugar and salt solutions on making vaccm to remove oxygen were studied. Besides that, the effects of different concentrations of disodium stannous citrate(DSC) and phytic acid were discussed. The best method of protecting color was selected: Guanxi pomelo pulp whose cyst membrance had been removed was vaccumed with 22% sugar solution at 0.075 MPa in the solid-liquid ratio of 1∶1 for 20 min, and 0.01% DSC was added in the sugar solution.The browning mechanism was preliminary investigated. The qualitative and quantitative analysis of pigments of pulp with and without color protection were studied. The result showed that five substances changed greatly before and after color protection. They were O-triglycosyl naringenin, naringin, acetyl naringin and two unknown substances. O-triglycosyl naringenin, naringin and acetyl naringin lost in the browning period. The color protection measure protected these substances so that made the color protection effect. A new substance was found in pulp without color protection, while there was none in the fresh pulp and a little in pulp after color protection. This may be due to the color protection measure which inhibited the formation of the substance so that played a color protection effect.The sugar components were prepared. The effects of different concentrations of citric acid,β-cyclodextrin and sweeteners were compraed. Under the fixed formula of 20% granulated sugar, 0.5%β-cyclodextrin, 0.3% citric acid, 0.01% DSC and 0.02% acesulfame, the optimal sensory quality of the products could be obtained.