1. Introduction
Vegetable soybean is a specialty food-type soybean harvested while the seeds are still immature at R6 stage It is similar to field matured soybean except for its larger seeds and lighter hilum color Vegetable soybean has advantages in sensory attributes over mature soybean, such as green color, soft texture, large seed size, slightly sweet taste, and less objectionable beany flavor. In addition, vegetable soybean is higher in nutritional content than mature soybean, including higher ascorbic acid and b-carotene contents, and lower amounts of indigestible oligosaccharides and anti-nutritional substances such as trypsin-inhibitors and phytates If properly stored, fresh vegetable soybean can retain its flavor and appearance for a short time period. The two most important sensorial attributes for vegetable soybean are sweetness and savory taste. The sweet taste comes from its high sucrose content, and thesavory taste is probably attributed to its amino acid composition For a desired appearance, vegetable soybean should have a bright green color without any defect and other color spot on the pods reported that vegetable soybean stored at 5 C for 10 days gradually decreased in green color, sucrose content, and seed weight.
Because of the short harvest period of vegetable soybean, proper processing is essential for year-round availability in the market. Combination of blanching in water and freezing has long been established as an excellent way of preserving vegetables by inactivating enzymes and decreasing the rate of enzymatic deterioration However, blanching vegetables improperly will affect their quality by softening the texture, browning the color, and decreasing thenutrient content. showed that steam blanching had advantages over water blanching because more soluble materials were lost during water blanching. showed that vegetable soybean blanched at higher temperatures for shorter time intervals had minimal loss of nutrients, including sugars, amino acids and vitamins. Nevertheless little research has been done comparing changes in sugar composition under different processing and storage conditions.
The objectives of this work were to investigate the change in soluble sugars of fresh vegetable soybean under different storage conditions, and the effects of different blanching methods on the soluble sugar content in vegetable soybean during frozen storage.