Abstract :
[en] Nowadays, there is an increasing interest for composite or gluten-free products due to some economic, nutritional reasons or the number of the celiac patient. The estimated prevalence of Celiac disease is about 1% of the general population, and it affects persons of any age, race, and ethnic group. Steamed bread is a traditional staple food of China, and has been consumed for at least 2000 years, taking up almost 40% of wheat consumption, and the popularity is increasing around the world. However, most traditional wheat steamed bread lack essential nutrients, including lysine, dietary fiber, vitamins, and minerals, etc. Therefore, the use of composite flour for steamed bread making has attracted great attention. Potato (Solanum tuberosum) is one of the most widely planted vegetables worldwide and is the only tuber used as a major food crop. Potato has a balanced amino acid composition, high total vitamin and mineral levels, and also contains phytochemicals such as polyphenols, polyamines, and carotenoids. However, the replacement of wheat flour is a major challenge for food technologist to produce the steamed bread with desirable quality and technological properties because that gluten is important to retain gas to obtain the desired volume and texture in a dough system. It is essential to form a strong protein network required for the desired viscoelasticity, and the easiest way to ensure the viscoelasticity properties is via the use of food hydrocolloids. Therefore, the aim of this work was to study the quality improvement of potato steamed bread using food hydrocolloids.
Firstly, the influence of potato flour on dough rheological properties and quality of steamed bread showed that the dough stability and specific volume of steamed bread were significantly decreased with the potato flour proportions increasing. Then we carried out the comparative study of the nutritional quality of steamed and baked breads from four potato cultivars because that the steamed and baked breads were two type of staple food in eastern and western countries, respectively. The results showed that potato flour addition increased the contents of dietary fiber, potassium, vitamin C, and total polyphenol contents and antioxidant activity. Hongmei was the optimum choose of the studied four cultivars, followed by Blue Congo, Shepody, and Atlantic, in terms of nutritional value. For the same cultivar, the nutritional value of steamed bread was higher than that of baked bread.
Secondly, the effect of different food hydrocolloids on the dough rheology and steamed bread quality parameters in composite and gluten-free formulations based on potato flour was studied. Compared to control, the food hydrocolloids addition significantly increased tightly bound water population, water absorption, starch gelatinization temperature, dough viscoelasticity, recovery percentage and development height. Little adhesion and aggregation of starch were observed and the density of potato protein bands was decreased when food hydrocolloids were added, suggesting that some aggregation formed between starch-hydrocolloids or proteins-hydrocolloids. Moreover, steamed breads with food hydrocolloids presented higher specific volume, lower hardness, and lower estimated glycemic index. In conclusion, food hydrocolloids showed the potential as a gluten replacement in composite or gluten-free potato steamed bread, particularly HPMC.
Thirdly, we optimized the formulations of gluten-free potato steamed bread. The optimal gluten-free steamed bread could be produced by adding 4.84 g/100g pregelatinized potato flour (PGPF), 1.68 g/100g hydroxypropylmethylcellulose (HPMC), 5.87 g/100g egg white protein (EWP) and 69.69 g/100g water based on potato flour, and this optimal bread was compatible with regular wheat bread in key sensory properties. Moreover, the optimized solid phase microextraction parameters (sample weight 2.42 g, extraction time 60 min, and extraction temperature 50°C) were adopted to determine the volatile compounds of gluten-free potato steamed bread. 72 volatile compounds were detected in the dough and crumb. The contents of alcohols, acids and esters increased significantly with the fermentation time increasing, which would improve the aroma of steamed bread.
However, further investigations are needed to elucidate the underlying mechanisms of action and the interactions with dough components and making additives. The other studies should be focused on technological approaches to improve steamed bread quality, which involved different flour particles, high pressure technology and application of sourdough.
