COLOR OF PROCESSED SWEET POTATOES: EFFECT OF ADDITIVES

The additives, ethylenediaminetetraacetic acid (EDTA), stannous chloride, citric acid, ascorbic acid and sodium bisulphite were added to syrup and vacuum packs of sweet potatoes. Addition of EDTA, SnCl₂, citric acid and sodium bisulphite was effective in decreasing darkening of the processed product. SnCl₂, EDTA and citric acid were also effective in preventing discoloration after exposure of the product to air. The action of the additives is attributed to a disruption of the reaction leading from oxidation of polyphenols to the production of dark-colored compounds.     

COLOR OF PROCESSED SWEET POTATOES: EFFECTS OF CAN TYPE

Sweet potatoes packed in four types of enamel-lined cans were darker in color and less attractive than those packed in tin-coated cans. The differences in color among can types was more pronounced after opening the canned product and exposure to air for an hour. The tin content of the product from the tin-coated cans was much greater than that from the enamel-lined cans. The brighter color of the product from the tin-coated cans is assumed to result from the substitution of tin for iron or other metals in the complex formed in the pheno-lase reactions.     

CONTROLLED HEAT PROCESSING OF JEWEL SWEET POTATOES FOR PUREE PRODUCTION1

‘Jewel’ sweet-potato slices 0.5 cm thick were precooked at 100, 125 and 150C for varying periods of time, finish-cooked for 15 min at 150C, and pureed. Selected chemical and physical properties of the purees were compared to a puree prepared from conventionally baked sweet potatoes (1.25 h at 195C). Purees from the controlled heat process were also compared to the baked puree by a sensory panel. Of all the treatments, puree from the 100C, 6-min precook treatment was the most silimar to puree from baked sweet potatoes with respect to chemical and physical characteristics. The sensory panel found the two purees to be different, but were equally divided when asked to express a preference. Subsequent analysis showed that the starch of the baked control had been more completely hydrolyzed than the starch of the other treatments. This was reflected by higher maltose, lower starch content and by decreased starch molecular size and viscosity of the control compared with the other treatments.     

不同品种甘薯色素紫外可见光谱性质研究

选用适宜天津种植的9种甘薯,分别用水和乙醇浸提甘薯色素,研究不同品种甘薯色素的紫外可见吸收光谱性质.结果表明,紫甘薯美国黑薯、德国黑薯和京薯6号水溶性色素吸收的最大吸收波长分别为538.5 mm、532nm和531.5 nm,花心薯水溶性色素吸收的最大吸收波长为525 nm,金海2号、日本黄薯、水果薯、苏薯8号、香蕉薯色素水浸提液没有吸收;美国黑薯、苏薯8号、德国黑薯、水果薯、香蕉薯、京薯6号、金海2号、日本黄薯、花心薯醇溶色素最大吸收波长分别为323、284.5 nm,424.5、288.5 nm,326、293 nm,424 nm,447.5、282.5 nm,326.5、297 nm,283.5 nm,281.2 nm,326.5、297 nm.德国黑薯和京薯6号甘薯色素应为同一种色素.     

酶法水解不同品种甘薯制备抗性淀粉

甘薯经过酶解、高温糊化、离心分离、酒精沉淀等工艺制备抗性淀粉.对于不同条件下α-淀粉酶、果胶酶及纤维素酶的酶解效果以及影响抗性淀粉产率的因素进行了研究.研究结果表明,α-淀粉酶、果胶酶和纤维素酶酶解甘薯最适温度,pH,最佳酶解时间,最适加量分别为:40℃,5,20min,200 U/mL;40℃,4.5,2h,150 U/mL;50℃.5,6h.15U/mL.甘薯抗性淀粉制备的最适条件为120℃,1.5h,甘薯液pH8,料液比1:12,在此条件下,不同甘薯抗性淀粉的制备率分另q是:苏薯8号1.3%;日本黄薯1.32%;京薯6号1.62%;香蕉薯1.83%;金海2号4.36%;水果薯2.83%;美国黑薯2.06%;德国黑薯1.86%;花心薯1.13%.金海2号甘薯抗性淀粉制备率最高.是适宜制备抗性淀粉的品种.     

EFFECT OF COOKING METHOD ON THE AROMA CONSTITUENTS OF SWEET POTATOES [IPOMOEA BATATAS (L.) LAM.]

To better understand the factors controlling the flavor of horticultural products, the effect of method of cooking on the volatile flavor of sweet potatoes was assessed. Volatile extracts from sweet potatoes cooked by baking, boiling, and microwaving were studied by GC, GC‐MS and GC olfactory assessment. GC‐olfactory analysis identified 37 compounds that were odor‐active, 36 of which were identified. Compared with conventional baking, boiling and microwaving yielded only 54.26% and 6.43% of the relative total yield of aroma‐active compounds, respectively. From aroma extract dilution analysis, four compounds contributed to the aroma from each cooking method. In addition, cooking method specific aroma contributing compounds accounted for the unique aroma of each of the cooked products. Thus the flavor of cooked sweet potatoes is dependent upon the method of cooking both on a sensory and chemical level.