GI is important parameter for the evaluation of the “Glycemic potential” of a food. It provides a practical guideline for diabetic people for selecting foods. Foods are categorized into three groups according to their GI . Food with GI < 55 is considered to be low GI food while high GI food is referred to the food with GI >70. Food with GI ranging between 55 and 70 is usually classified as medium GI food. Some studies suggested that whole-grain foods may reduce the glycaemic response and reduce the risk of diabetes [12, 13]. That was apparently due to cereal fiber intake. Other studies suggested that the traditional baguette have lower GI in type 2 diabetes subjects than other varieties (classic baguette, loaf of wholemeal bread, loaf of bread fermented with yeast or with leaven, sandwich). These differences might be explained in bread processing and fermentation procedure rather than fibre or resistant starch content . Processing and fermentation procedure of the steamed bread is different from that of the bread. Previous studies have showed that GI of steamed bread made from bread wheat was 98.34, which was classified as high-GI food , Yang et al.  reported that GI of steamed bread was 88.1±20.2. Thus, white wheat bread is usually defined as a high GI food . In this study, glucose was used as the reference food (only one determination). The GI of steamed bread made from Jizi439 were compared with other varieties, and found that GI of Jizi439 was significantly lower than that of other wheat varieties.
The carbohydrate content of a food and its composition play a major role in influencing the postprandial plasma glucose. Starch is an important carbohydrate source in the human diet. Some studies showed that higher amylose usually results in lower glucose responses [28, 29]. Behall et al. reported that high amylose(70% amylose) crackers were significantly lower than the high amylopectin (70% amylopectin) crackers. The present results demonstrated that Jizi439 contains 31.0% amylose (amylose/total starch). Since most wheat cultivars contain 16.18-31.79% amylose in China , Jizi439 is considered to be a high amylose wheat variety. This may be the one of the reasons that GI of Jizi439 was lower.
The medical evidence showed that the organic chromium was one of the essential microelements for human body, and played a very important role in maintaining and regulating proper levels of carbohydrate, lipid metabolism and enhancing insulin signaling [26, 31, 32]. In vitro and in vivo studies suggested that chromium supplements, particularly niacin-bound chromium and/or chromium-nicotinate, may be effective in attenuating insulin resistance and lowering plasma cholesterol levels . In contrast,a few of studies showed that chromium supplementation did not improve glycemic control in type 2 diabetes [33, 34]. Nevertheless, most research believed that supplemental Cr is beneficial to diabetes patients [16, 17, 31, 32]. Jizi439 could provide a microelement supplement. This wheat variety offered medicational as well as nutritional values, which made it an ideal food source to prevent diabetes, cardiovascular diseases and enhancing immunity. Therefor, it should be widely used as unique raw material to make various wheat-based end-products, such as bread, steamed bread and noodles.
It was reported that the intake of buckwheat could effectively reduce diabetes symptom . A test that compared the effect of whole buckwheat on plasma glucose with the bread made from refined wheat flour indicated that buckwheat significantly lowered plasma glucose responses ; Skrabanja et al.  have found that buckwheat may be beneficial to diabetes. In a placebo (sucrose) -controlled study of streptozotocin-diabetic rats, a single dose of buckwheat seed extract lowered plasma glucose levels by 12-19% within 90 and 120 min after administration. In present study, postprandial 2 h plasma glucose level of Jizi439 was lower than that of buckwheat. Therefore, Jizi439 should be also beneficial to diabetes.