Tea compound-saliva interactions and their correlations with sweet aftertaste.

Huigan is an important sensory attribute which is commonly used as a quality indicator evaluation of tea products. Previous studies showed a strong correlation between the lubrication behavior of saliva-tea compound mixture and the sensory perception of Huigan from trained panelists. This work was further designed to investigate how the effect of tea consumption on the rate of saliva secretion and its functional properties including total protein content of saliva (TPC), salivary α-amylase (AMY) and lipase activity (LP). A quartz crystal microbalance with dissipation monitoring (QCM-D) was applied to reveal the adsorption behavior of human whole saliva and how the salivary film is affected by the presence of tea compounds. Results showed a significant positive correlation among TPC, LP and Huigan intensity for subjects who are Huigan-sensitive. Compared to the desorption of salivary film, the desorption of saliva-EC/EGC (epicatechin/epigallocatechin) mixture from the gold surface by QCM-D observation showed a significant effect on Huigan intensity in sensitive group when comparing to the salivary layer (blank).

Oral physiological characteristics among Chinese subjects in the eastern region of China.

OBJECTIVES: With an increasing number of elderly in China, it becomes imperative to establish a comprehensive understanding of their physiological capabilities and investigate fundamental mechanisms underpinning the discrepancies between Chinese individuals and other ethnical groups, which will facilitate government policymaking, design and development of special food products. DESIGN: In this study, 100 healthy Chinese subjects in the eastern region of China (22-89 years old) were recruited with full consent, then divided into young adult, middle-aged and elderly groups. Subjects' maximum biting force (MBF), maximum tongue pressure (MTP), maximum oral volume (MOV), and saliva flow rate were recorded. Unstimulated (US) and stimulated (SS) saliva were collected. Subjects were then objectively clustered into 3 different levels of oral processing capability. A total of 10 young subjects from two different clusters were selected for chewing efficiency (CE) determination. CONCLUSIONS: With increased age, there is a decline in subject's dental status, MBF and MTP. Gender affects greatly on MOV; males have larger MOV. No significant effects on SS and US flow rate were found with age and gender. The finding of a similar CE and differences in overall capability in relevant physiological variables (MBF and MOV in young adults) suggest that the degree of CE is not determined by a total capability of various oral physiological variables. In contrast, the findings suggest that CE will be non-impaired as long as each of the relevant physiological variables (i.e. dental status, MBF) operates at a supra-threshold level.

Saliva could act as an emulsifier during oral processing of oil/fat.

Human saliva is a fluid naturally secreted in the oral cavity that interacts with food and food components for bolus formation, structure degradation, as well as lubrication. Because of the presence of salivary proteins, we speculate that saliva could also function as an effective emulsifier during oral processing of oil/fat. In this preliminary work, experiments were then designed to test this hypothesis. Whole human saliva from three healthy subjects were collected and analyzed for protein content, surface tension, and molecular weight distribution. Saliva emulsions were obtained both in vitro one and in situ for all three participating subjects. Droplet size distribution, zeta potential, and microstructure of such emulsions were examined immediately after the emulsification. Results show that stable saliva emulsions can be produced during oral processing of either pure oil (rapeseed oil) or fat food (pork belly in this work). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that protein fractions of 27 and 55 kDa molecular weights were favored for emulsion formation. This work suggests that human saliva could function as an effective emulsifier and oral emulsification could be an important mechanism for the oral processing of oil/fat. Despite being preliminary, findings from this work provide a new scientific insight to our understanding of the oral behavior of oil/fat and their sensory perception. PRACTICAL APPLICATIONS: Food industry is currently under a growing pressure to use novel techniques and ingredients to minimize the use of oil/fat in food products but without compromising its sensory quality. However, food industry has limited progresses because of the lack of understanding of the mechanisms of oral sensation and perception of oil/fat. Whereas there have been extensive debates about the sensory mechanisms of oil/fat, this work takes a step back by examining the oral behavior of oil/fat. Findings show that saliva can actually function as emulsifier to oil/fat, which means that ingested oil/fat will be dispersed and converted into an emulsion at the oral stage. The findings from this work offer food industry new insight on the sensory mechanisms of oil/fat.