Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres Role of biochemical and mechanical disintegration on β-carotene release from steamed and fried sweet potatoes during in vitro gastric digestion Geeshani Somaratne a,b , Aiqian Ye a , Francoise Nau d , Maria J. Ferrua c,e , Didier Dupont d , R. Paul Singh c,f , Jaspreet Singh a, ⁎ a Riddet Institute and Massey Institute of Food Science and Technology, Massey University, Palmerston North, New Zealand b Department of Food Science and Technology, Faculty of Agriculture, University of Peradeniya, 20450, Sri Lanka c Riddet Institute, Massey University, Palmerston North, New Zealand d STLO, INRAE, Institut Agro, 35042 Rennes, France e Fonterra Research and Development Centre, Palmerston North, New Zealand f Department of Biological and Agricultural Engineering, University of California, Davis, CA, USA ARTICLE INFO Keywords: Stomach β-carotene Cell wall breakdown Softening Mechanical forces Human gastric simulator ABSTRACT The role of biochemical and mechanical disintegration on β-carotene release from steamed sweet potatoes (SSP) and fried sweet potatoes (FSP) during in vitro gastric digestion was investigated. Results revealed that, in the absence of mechanical forces generated by the stomach, biochemical digestion did not have a great effect on the breakdown of cell walls within the sweet potato food matrix and the release of ß-carotene was similar in both SSP and FSP. Cell wall in the plant-food may act as a physical ‘barrier’ towards the action of gastric juice and to the release of nutrients into the gastric digesta. However, FSP underwent quicker softening and collapse during in vitro gastric digestion compared to the compact and denser structure of SSP. This may explain the faster cell wall breakdown and subsequent β-carotene release from FSP cellular matrix than SSP when mechanical forces are applied as in the human gastric simulator (HGS). 1. Introduction β-carotene is the predominant natural pigment principally re- sponsible for the characteristic deep-orange colour of sweet potatoes (Bengtsson, Brackmann, Enejder, Alminger, & Svanberg, 2010; Tumuhimbise, Namutebi, & Muyonga, 2009). It has attracted con- siderable attention as epidemiological evidence continues to suggest that it may provide protection against cancers and other degenerative diseases (Low, D'Arcy, & Gidley, 2015). This could be due to its bio- logical and physicochemical properties, especially related to its effects as a natural antioxidant and its provitamin A activity (Low et al., 2015; Schweiggert et al., 2014). Orange-fleshed sweet potatoes and related products are one of the major sources of β-carotene compounds in the human diet and they can be an efficient way to deal with vitamin A deficiency (Islam, Nusrat, Begum, & Ahsan, 2016). β-carotene is physically encapsulated within the parenchyma cells of sweet potato tubers (Mennah-Govela & Bornhorst, 2016a, 2016b). Thus, bioaccessibility of β-carotene requires the breaking down of cell walls for the release from the food matrix during food processing and/or digestion and subsequent absorption in the small intestine (Mennah-Govela & Bornhorst, 2016b; Tumuhimbise et al., 2009). The major physicochemical transformation of food matrices occurs in the stomach after oral processing (Kong & Singh, 2008; Singh, Ye, & Ferrua, 2015). Gastric digestion combines several physicochemical processes (diffusion of gastric fluid, heat transfer, fragmentation, dis- solution, enzymatic reactions, etc.) that lead to the formation of a chyme before its entry into the small intestine (Kong & Singh, 2008, 2009a; Somaratne et al., 2020a). Diffusion of gastric fluid along with acid hydrolysis and enzymatic action help to soften food texture, thus improving the disintegration and nutrient release rate (Drechsler & Bornhorst, 2018; Kong & Singh, 2009b). Although the effect of bio- chemical and mechanical disintegration kinetics in different model food systems (i.e. egg white gels, whey protein gels, dairy gels etc.) on nu- trient release during gastric digestion has extensively studied (Guo et al., 2015; Guo, Ye, Lad, Dalgleish, & Singh, 2014; Le Feunteun et al., 2014; Somaratne et al., 2019, 2020b, 2020c), the mechanism by which the diffusion of the gastric juice affects the mechanical disintegration of https://doi.org/10.1016/j.foodres.2020.109481 Received 6 April 2020; Received in revised form 17 June 2020; Accepted 23 June 2020 Abbreviations: SSP, Steamed Sweet Potatoes; FSP, Fried Sweet Potatoes; HGS, Human Gastric Simulator; LM, Light Microscopy ⁎ Corresponding author. E-mail address: J.X.Singh@massey.ac.nz (J. Singh). Food Research International 136 (2020) 109481 Available online 27 June 2020 0963-9969/ © 2020 Elsevier Ltd. All rights reserved. T