JIA-2019-11

2653 Ji-Eun Kim et al. Journal of Integrative Agriculture 2019, 18(11): 2652–2663 bread are flour (100%), water (50–60%), salt (1%), yeast (1–4%), sugar (5–10%), and shortening (3–5%) are added for texture, but baking powder is only used for Musimanju of Japan (Huang and Miskelly 2016). Steamed bread is used as the staple food in northern China, the main wheat producing region, and served as warm meal (Huang and Miskelly 2016). Protein content is different according to grain hard types, hard and soft type wheat (Issarny et al . 2017). Generally, soft type wheat is suitable for cookies and low level protein, about 8–10%, while hard type wheat is suitable for bread and high level of protein, about 10–14% (Huebner et al . 1999; Park et al . 2006; Delcour et al . 2012; Issarny et al . 2017). The appropriate wheat flour for northern-style Chinese steamed bread (NSCSB) is known to have 10% of protein content and medium gluten strength (Lin et al . 1990). The research for improvement of NSCSB quality is actively underway not only in China, the main wheat consumer, but also in the USA, Canada, and Australia, the major countries exporting wheat to China. The additional mixing for dough, unlike conventional dough mixing for NSCSB, has recently been proposed to improve the smoothness and brightness of surface of steamed bread (Huang et al . 2015). Korean style steamed bread (KSSB) is being consumed as snack during winter, and the main ingredients are dough stuffed with one of red bean paste, vegetable and meat, and yeast and chemical inflating agent are used for the dough making (Kim et al . 2001). KSSB is good to have white and glossy surface and soft inner texture and not to have cohesiveness or stickiness (Kim et al . 2001). KSSB reacts so sensitively to flour property and fermentation condition that the phenomenon falling in or having wrinkles occurs often. Generally, it is known that the more steamed bread has protein content, the more these phenomena happen. The recent research for KSSB is being focused on the improvement of physiochemical properties, antioxidant activity and shelf life by addition of supplementary materials. KSSB has been produced at random according to the experience of the manufacturer and the situation because the quality standard of flour suitable for KSSB or the method of manufacturing for KSSB is not specifically provided (Kim et al . 2001). The purpose of this study was to investigate the effect of wheat flour characteristics on the characteristics of steamed bread, NSCSB and KSSB, made from 11 different Korean wheat cultivars and to understand the major factors affecting the manufacture and quality of steamed bread. 2. Materials and methods 2.1. Materials Eleven Korean wheat cultivars were sown in randomized complete blocks with three replications in the Upland Crop Experimental Farm of the National Institute of Crop Science, Rural Development Administration (Korea) in 2016/2017 on 50% clay/loam soil. The seeds were sown in late October, and each plot consisted of three 4-m rows spaced 25-cm apart. These plots were combine-harvested in mid-June for 2 yr. Prior to sowing, fertilizer in the ratio of 5:7:5 kg per 1 000 m 2 (N:P:K) was applied, while weeds, insects, and disease were stringently controlled. No supplemental irrigation was applied. Grains from each plot were dried using forced-air dryers and bulked from replications to provide grains for milling. 2.2. Analytical methods Wheat grain was milled using a Bühler experimental mill, based on the American Association of Cereal Chemists International (AACCI) Approved Method 26–31.01 (AACCI 2010). A total of 2 kg of wheat grain was tempered to 15% moisture prior to milling for 12 h and milled with a feed rate of 100 g min –1 and with roll settings of 8 and 5 in break rolls and 4 and 2 in reduction rolls. Moisture, ash content, protein content and sodium dodecyl sulfate (SDS) sedimentation test of wheat flour were determined according to AACCI Approved methods 44–15.02, 08–01.01, 46–30.01 and 56– 70.01, respectively (AACCI 2010). The SDS sedimentation volume of flour was determined both on a constant flour weight (3 g) basis and on a constant protein (300 mg) basis. Amylose and damaged starch contents were determined using the methods described by Gibson et al . (1992, 1997), respectively, using enzymatic assay kits (Megazyme, Bray, Ireland). Flour particle size distribution was measured with an LS13320 multi-wavelength laser particle size analyzer (Beckman Coulter, Brea, CA, USA) according to AACCI Approved Method 55–40.01 (AACCI 2010). Flour color was measured with a colorimeter (CM-2002, Minolta Camera, Osaka, Japan) using an 11-mm measurement aperture. Whiteness index was calculated according to Nguimbou et al . (2012). Solvent retention capacity (SRC) tests were conducted according to the AACCI Approved Method 56–11.01 using 5% lactic acid, 5% sodium carbonate and 50% sucrose solutions, and distilled water (AACCI 2010). Dough mixing properties were determined using a 10-g Mixograph (National Mfg. Co., USA) following AACCI Approved Method 54–40.02 (AACCI 2010). Starch was fractionated from flour (100 g, dry base, db) according to the method described by Czuchajowska and Pomeranz (1993). Briefly, starch separated from gluten was purified by multiple washing with distilled water. The purified starch was air-dried at 24°C for 3 d and ground with a cyclone sample mill (Udy, Fort Collins, Co., USA) fitted with a perforated