Texture evaluation of rice cake for people with mastication difficulty and dysphagia by instrumental analysis and human measurement during eating

Abstract

Rice cake (mochi) is a difficult food to chew and swallow．Recently the food industry has produced some mochi-like products by modifying the texture for the elderly or people with chewing and swallowing difficulties．We compared the texture of standard rice cake and a modified product．An instrumental two-bite test was adopted to characterize sample texture including firmness，cohesiveness，adhesiveness，and compression energy．The modified product was softer and had less cohesiveness and bite energy than standard rice cake．However，the adhesiveness value of the modified product was similar to that of the standard．The modified product exhibited more stable texture when cooking time and storage time after cooking were varied． We also recorded mastication and swallowing behaviors of 11 normal women eating the two rice cake samples．Electromyography from both sides of the masseter muscles and suprahyoid musculatures；larynx movement by an array of three small pressure sensors placed on the thyroid cartilage，and swallowing sound beside the cricoid cartilage，were measured．Electromyography during chewing revealed that the modified product required shorter mastication time (60％ of the standard) and smaller amplitude of jaw-closing muscles (78％) than the standard rice cake．Those resulted in much less mastication effort until swallowing (57％ for the masseter muscles，and 50％ for the suprahyoid musculatures，of the standard)．The modified product also showed less activity (69％ of the standard) of the suprahyoid musculatures at the beginning of the swallowing corresponding to less adhesiveness．However，similar larynx movement and sound for swallowing were observed for both samples．Human measurement provided more direct evidence for difficulties in mastication than instrumental texture analysis，but it showed less difference between the two samples in swallowing．As healthy subjects could change the manner of mastication according to sample texture，there may not be significant differences between boli of different rice cake samples after swallowing began．