Natural eating behavior of two types of hydrocolloid gels as measured by electromyography: Quantitative analysis of mouthful size effects

Abstract

The objectives of this study are to identify mechanical properties that dictate natural oral processing of soft solid foods and to quantify the effects of mouthful sizes. Two types of hydrocolloid gels with similar fracture loads but different elastic moduli and fracture strains were prepared using agar (A) or a mixture of konjac mannan, κ-carrageenan, and locust bean gum (K). Subsequently, 3, 6, 12, and 24 g mouthfuls of A and K gels were randomly served to subjects and the effects of mechanical properties and mouthful sizes were quantitatively analyzed within an individual. Electromyographic (EMG) activities of both masseter muscles and the suprahyoid muscle were recorded as jaw-closing and jaw-opening muscles, respectively. Total 33 EMG variables relating mastication and swallowing difficulties were classified into six groups by influences of gel types and mouthful sizes. Despite similar fracture loads, K gels with greater fracture strain and work required more mastication effort and less swallowing effort than A gels, which had higher elastic modulus. Doubling of mouthful sizes between 3 g and 24 g increased oral processing times and the numbers of chewing actions and swallows by 1.4 fold. These variables were approximately proportional to 0.7 of the power of the mouthful mass, and they can be predicted using this relation. Mastication effort exhibited lower dependence on sample mass than the three variables and durations and muscle activities per masseter muscle action did not vary significantly with mouthful sizes and gel types.