BOLUS MOISTURE CONTENT OF SOLID FOODS DURING MASTICATION LIDIA MOTOI 1,3 , MARCO P. MORGENSTERN 1,3 , DUNCAN I. HEDDERLEY 2 , ARRAN J. WILSON 1 and SINAG BALITA 1 1 The New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch Mail Centre, Christchurch 8140, New Zealand 2 The New Zealand Institute for Plant & Food Research Limited, Palmerston North, New Zealand KEYWORDS Bolus, mastication stages, moisture content, saliva 3 Corresponding authors. TEL: +64-3-3259481; FAX: +64-3-3252074; EMAIL: lidia.motoi@plantandfood.co.nz; marco.morgenstern@plantandfood.co.nz Accepted for Publication July 8, 2013 doi:10.1111/jtxs.12036 ABSTRACT Saliva addition plays an important role in bolus formation. During chewing, food breaks down, exposing food particles to saliva. The aim of this study was to explore and understand how bolus moisture content changes during the oral pro- cessing of solid foods. Twelve subjects chewed commercially produced solid foods; the boluses were collected at different stages of the mastication process, including the swallowing point, and all of the boluses produced were analyzed for their moisture content. The chewing sessions were recorded on video, enabling the number of chews to be assessed for each subject and food type. Results showed that moisture content of boluses during mastication increased linearly at a rate depending on the subject and food types studied. It was found that for the food types studied, an increase in initial food moisture content increased the bolus moisture content at the swallowing point. PRACTICAL APPLICATIONS Sensory perception experienced during oral processing of foods is through sensing the bolus properties, which change continuously in between ingestion and swal- lowing. Understanding changes in bolus moisture content, the role of food struc- ture and effects on sensory perception can help in designing foods with predictable sensory attributes. This study demonstrated that while saliva additions vary between people and food types, they increase linearly during mastication. Changes in bolus moisture content during mastication could be used to guide the design of solid foods with target properties. INTRODUCTION During oral processing a solid food is transformed into a bolus (Bourne 2002) until the consistency of the bolus reaches conditions for safe swallowing (Prinz and Lucas 1995; de Wijk et al. 2003; Chen and Lolivret 2011). Mastica- tion involves complex oral processes (Engelen et al. 2007; Chen 2009; Chen and Engelen 2012), including breakdown of the food, jaw movements, moistening, lubrication and dissolution by saliva as well as heating and shearing of the food. Numerous studies (Kohyama et al. 2002, 2008; Peyron et al. 2002; Piancino et al. 2008) have investigated the oral processing parameters of solid foods, including the number of chews, chew frequency, chew time, oral residence time, jaw movements, muscle activity, friction and many other parameters (Riqueto Gambareli et al. 2007; Sazonov et al. 2008; Moritaka and Nakazawa 2010) in order to determine how changes in food, when processed in the mouth, relate to texture perception. It has been documented that oral food manipulation has an impact on the way food is per- ceived (Mioche 2004; Engelen et al. 2007; Lenfant et al. A journal to advance the fundamental understanding of food texture and sensory perception Journal of Texture Studies ISSN 1745-4603 1 Journal of Texture Studies •• (2013) ••–•• © 2013 Wiley Periodicals, Inc.