Journal of Cereal Science 98 (2021) 103176 Available online 22 January 2021 0733-5210/© 2021 Elsevier Ltd. All rights reserved. Effect of type-2 resistant starch (high-amylose maize starch) on the physicochemical, nutritional, in vitro starch digestibility and estimated glycaemic properties of Chinese steamed buns Noraidah Haini , Lee Jau-Shya , Ramlah George Mohd Rosli , Hasmadi Mamat * Faculty of Food Science and Nutrition, Universiti Malaysia Sabah, Jalan UMS, 88400, Kota Kinabalu, Sabah, Malaysia A R T I C L E INFO Keywords: Physicochemical properties Starch digestibility Estimated glycaemic index High amylose maize starch Steamed bun ABSTRACT Resistant starch (RS) is a portion of starch that resists enzymatic digestion. It is applied in the production of Chinese steamed bun (CSB) to increase daily fbre intake. In this study, the incorporation of type-2 RS known as high-amylose maize starch (HM) (5%, 10%, 15%, 20%, 25% and 30%) and its effect on the rheological and physicochemical properties, nutritional values, in vitro starch digestibility and estimated glycaemic index (eGI) properties of CSBs were determined. High HM incorporation levels increased RS and dietary fbre contents and reduced the pasting viscosities and calorifc values of CSBs. The addition of HM-enriched RS also affected total starch content and eventually resulted in the decreased susceptibility of starch to digestive enzymes in vitro. The decrement in starch hydrolysis rate markedly reduced the eGI of HM-containing CSBs. The incorporation of 25% HM into CSBs (eGI = 68.45) could be applicable in developing a nutritious and medium-eGI CSB without jeopardising desirable physical attributes. 1. Introduction Diets rich in fbre are benefcial in preventing metabolic diseases, such as diabetes, obesity and hypertension, as well as abate colon cancer and constipation. The global status report on noncommunicable diseases shows that people consume dietary fbre (DF) at amounts less than the recommended serving (20–40 g) (WHO, 2014). Concurrent with WHO recommendation policies, one strategy to increase the intake of DF is through the fbre-enrichment of functional food that retains consumer appeal. This functional food can be derived from a fbre ingredient known as resistant starch (RS). RS refers to the portion of starch that resists enzymatic hydrolysis and is left to ferment in the colon; it is thus regarded as an integral component of DF (Amaral et al., 2016). RS possesses unique character- istics, such as white colour, bland favour and fne texture, that are useful for maintaining the physical attributes and sensory acceptance of a food product. Incorporating RS into food products is a practical approach towards replacing refned carbohydrates because RS increases fbre content and tastes better than conventional insoluble fbre, which exhibits a coarse texture and unpalatable favour (Shukri et al. 2017). Moreover, foods rich in RS have lower calories and glucose response than rice, which is high in digestible carbohydrates. Considering the technological and commercial values of RS, the use of RS in bakery products, such as breads (Arp et al., 2018b; Collar et al., 2014; Sanchez et al., 2014; ¨ Oztürk et al., 2009), cakes (Magallanes-Cruz et al., 2020), muffns (Sanz et al., 2009) and biscuits (Laguna et al., 2011), has been extensively studied. Those studies generally reported that food products modifed with RS show improved dough handling ( ¨ Oztürk et al., 2009), increased total dietary fbre (TDF) content (Mag- allanes-Cruz et al., 2020) and low estimated glycaemic index (eGI) and retain their textural and sensory qualities (Arp et al., 2018b). To the best of our knowledge, literature on the incorporation of RS into steamed products is limited. Therefore, this study aimed to explore the effect of RS in Chinese steamed buns (CSBs). CSBs are a famous Asian staple food originating from China (Zhu, 2014), with as many as 17.10% of Malaysians eating one serving of CSB per day (Kasim et al., 2018). Shukri et al. (2017) reported that the addition of 15% cross-linked RS is suitable for increasing the fbre content of steamed buns while exerting negligible effects on appearance and sensory attributes. The incorporation of 5%–10% high-amylose maize starch (HM) into steamed buns successfully imparts nutritional value without altering textural, sensory and shelf-life qualities (Wang et al., 2017). However, Guan (2007) reported that the substitution of 5% RS (extracted from buckwheat) into steamed buns results in reduced * Corresponding author. E-mail address: idamsah@ums.edu.my (H. Mamat). Contents lists available at ScienceDirect Journal of Cereal Science journal homepage: http://www.elsevier.com/locate/jcs https://doi.org/10.1016/j.jcs.2021.103176 Received 23 October 2020; Received in revised form 14 January 2021; Accepted 18 January 2021