Relationships Between Mechanical Properties Obtained from Compression Test and Electromyography Variables During Natural Oral Processing of Gellan Gum Gels

Abstract

AbstractThe objective of this study was to quantify natural eating behavior of soft solid foods and identify a mechanical property of food that has the strongest influence on mastication in humans. Electromyography (EMG) of both masseter and suprahyoid muscles was performed to quantify the muscle effort required to naturally masticate five gellan gels. The gels were categorized into two groups; those with (1) similar fracture strain and three different fracture loads (F1 < F2 < F3), and (2) similar fracture load and three different fracture strains (S2 < F2 < E2). True stress of these gels was evaluated using video imaging during an instrumental compression test. EMG variables corresponding to masticatory effort increased with fracture load and with decreasing fracture strain under similar fracture loads of the gellan gels. Fracture load affected the natural eating behavior of the gels more than fracture strain. True stress, in particular true fracture stress, was a better indicator of mastication requirement than load. According to texture, human subjects changed their method of oral processing for the consumption of a small piece of gel from compression between the tongue and hard palate to mastication using the teeth. Once the method was chosen based on the mechanical properties under small deformation before fracture, muscle effort for oral processing highly correlated with true fracture stress but did not significantly correlate with modulus or fracture strain.Practical ApplicationsThe requirements for appropriate care food that can be consumed using compression by the tongue and hard palate without using the teeth have increased because the numbers of elderly people with poor mastication performance has increased in an aging society. The oral method changed from compression between the tongue and hard palate to mastication by the teeth with increasing true fracture stress of gels. Mastication effort quantified by electromyography highly correlated with the true fracture stress, but inferior correlation was observed with fracture load and no correlation with other mechanical properties, such as modulus and fracture strain. A simple compression test with video imaging can successfully measure the true stress of food samples. True fracture stress from the compression test was the best single parameter that explained the mastication effort during the natural eating behavior of soft gels.