Abstract
The potential of fermentation broth of Ganoderma lucidum (FBG) in improving the quality of Chinese steamed bread (CSB) was firstly evaluated. The sensory quality scores of CSB treated by FBG are significantly higher than that of CSB in the control, and texture profile analysis also indicates the increase of CSB hardness and chewiness caused by FBG. Observation on micro-structure of CSB shows that formation of larger pores and expansion of starch granules are the important reasons for the improvement of CSB specific volume (volS), and granule expansion is due to that gluten network distributed in CSB is destroyed as a result of cross-linkage of flour proteins catalyzed by laccase, which makes starch granules releasing from the network easily contact with steam or other enzymes during the proofing and steaming of dough. Moreover, FBG contains amylases which not only convert amylopectin to amylose, but also degrade starch to glucose, maltose and polysaccharides, correspondingly resulting in changes of amylose/amylopectin (Ae/An) ratio of flour and CSB volS, and the latter is because more CO2 produced by the yeast during CSB making leads to the larger pore area in crumb. Both hardness and chewiness are determined by the comprehensive effect of protein cross-linkage, Ae/An ratio and volS change, and this viewpoint gives a logical explanation for the effects of 0.025–0.10 ml/g of FBG on hardness and chewiness of CSB.
Highlights
Chinese steamed bread (CSB) is a fermented wheat flour product
Submerged cultivation and zymogram analysis of laccase The G. lucidum used in this work is a good laccase producer (Wang et al 2013), and laccase activity was Sensory evaluation CSB quality assessment is largely based on personal judgment and subjective qualitative evaluation, and the results reflect the consumer preferences (Shah et al 2006)
The previous literature has proven that laccase is able to improve CSB hardness by crosslinking proteinaceous food matrices (Selinheimo et al 2006; Minussi et al 2002), and in this work, both microstructure observation and SDS-PAGE analysis show the ability of laccase in F BG to cross-link flour proteins
Summary
Chinese steamed bread (CSB) is a fermented wheat flour product. Its preparation process is similar to that of western-style pan bread, but the final product is steamed in a steamer, not baked in an oven. Steaming process has an advantage over baking since it uses water vapor temperature which is much lower than baking temperature (around 180–220 °C). Nutrients might be better retained when compared to the baked bread (Victoria et al 2013). Within the intercommunication of food culture among different countries, CSB has spread from China to other Asian, North America and European countries (Wu et al 2012). In CSB making process, protein and starch, as the main
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