脫水鳳梨之製造及其在貯藏期間維生素C含量之變化試驗

A Study on the Dehydration of the Pineapple and Variation of the Vitamin C Content of the Dehydrated Pineapple with Different Packages during the Storage Period

錢金鎖(C. S. Tsien) ； 陳景福(G. F. Chen)

《中華農業研究》 8卷1期 (1958/12) Pp. 11-16

https://doi.org/10.29951/JARC.195812.0002

並列摘要

The canned pineapple has become an important food industry in Taiwan. About more than 900,000 wooden cases of canned pineapple were exported each year. In order to maintain the best quality for foreign trade, only whole slices are selected to fill into cans, but the broken or quarter slices and pieces are remained an appreciable quantity in the course of canning. Those can be utilized as raw materials for dehydration. Many experiments have been done for the dehydration of pineapple during the past several years for its economical importance. Modified method of dehydrating pineapple is as follows:
(1) Peeling and Coring: This is done by machine, the peeling and coring being accomplished in one operation. The peeled trimmed fruit may be sliced into 1/16 part of the original slice or diced in one oubic centimeter cubes.
(2) Steam blanching: Diced slices should be steamed for 6 minutes before sulfiting, this is necessary in order to get a translucent product.
(3) Dipping: After blanching, one group is immersed in a 0.3% of sodium sulfite or sodium bisulfite solution (which based on the weight of fruit meat), and the other group is not immersed in sodium sulfite solution as control. Afterwards both groups are wholly dipped into the sugar solution (that concentration is 60 Brix) for twelve hours.
(4) Dehydration: After dipping, both groups are ready for dehydration. This is preferably done in a two-stage tunnel dehydrator. Each tray is loaded not exceeding 1.5 pound per square foot of drying area. In the first stage, the drying temperature should be kept in 180°F. about 3 hours, and in the second stage, it should be continuously dried at 150°F. until the moisture content is below 15%. After dehydration is complete, then packing and storing.
As regard for the packing and storing of the dehydrated products, three differerent packing materials are used for the dehydrated pineapple in this experiment. They are polyethylene bags, polyethylene boxes and paraffined paper boxes. Before packing, dehydrated pineapple are often fumigated with methyl bromide. After fumigation, the products are field and pressed into insect-proof bags and boxes, and subsequently the containers should be heat-sealed, but in the case of polyethylene boxes covering with lid, itis coated with the laminated cellophane. Finally storing the dehydrated products in the common storage warehouse for one year. The Vitamin C or ascorbic acid is determined at the end of 3 months, 6 months, 9 months and one year respectively.
Results of this experiment are in the following:
1. Change of the color: During the process of dehydration, if the drying temperature exceeds 200°F., it tends to accelerate the rate of color change from yellow to yellowish brown. It is necessary to avoid high humidity during drying, otherwise the discoloration will result. Furthermore, when the product is in the high temperature, the inversion of sugar will be increased and finally invert sugar (the mixture of glucose and fructose) will be produced, Meanwhile the sugar became easily caramel.
2. After the blanching, if the products is treated with sodium sulfite and placed in a cool place, and if the moisture coutent is not increased, the color can be maintained more than one year. If the products are exposed directly to sunshine, the color will be changed within four hours. It is assumed that light probably destroyed the color constitution in the dehydrated pineapple.
3. Color and flayer of dehydrated products, which are not treated with sodium sulfite solution, changed after 3 months’ storage; but treated with sodium sulfite, are not changed even after 6 months' storage. The former is entirely decayed, while the latter has been kept in good quality.
4. Dehydrated products which are packed with polyethylene boxes are not changed after one year's storage. Those packed with other two kinds of containers became soft with a decreasing of palatability, but the color is not changed.
5. Temperature is an important factor in the storage life of dehydrated products. The lower the temperature of the storage, the longer the storage life. During the storage of dehydrated pineapple, there is a decrease in Vitamin C content and palatability, the extent of this decrease depends upon the storage temperature, moisture content of the products. The reduction of Vitamin C content in the three different packages are made during this experiment. In the common storage room, there are over 77% of the Vitamin C lost in all package treatments. There is no significant difference in the reduction of Vitamin C among the three packaged materials. Packing with polyethylene boxes give 77.11% of Vitamin C loss, while those packed with polyethylene bags give a 77.93% of loss.