Identifying Human Sensitivity Towards Monosodium Glutamate using Tomato soup as a model

Abstract

Monosodium Glutamate (MSG) is the world's most widely used flavour enhancer. It was first identified by Prof. Ikeda in 1907 and was commercialised by Mr. Suzuki under the company name of AJI-NO-MOTO two years later. This compound is associated with the famous 'Chinese Restaurant Syndrome' which is experienced 15 to 20 minutes after consumption of food at a Chinese Restaurant. The sensory characteristics of this compound are referred to as umami or savoury and are distinct as compared to the basic four tastes. Prof. Ikeda in 1909 identified the threshold value of MSG to be approximately 1g/3L (0.3g/1L). It has been over 100 years since this threshold value was estimated and value may be changed as we get more exposure to this compound in our foods. Therefore, one of the objectives of this study was to identify human sensitivity threshold to this compound in the current time. The second objective of the study was to evaluate consumer perception of MSG. In the threshold study, the Single Interval Adjustment Matrix(SIAM) procedure was applied as this method is proven to be a recent, robust and well developed method. A total of 15 participants from the age group of 20-35 years were selected to take part in this study. They attended 15 tasting sessions over a period of 15 weeks and tomato soup was used as a stimuli. The results show that during the first week of study, the participants had difficulty tasting 0.5g of MSG per1L of soup, but as the weeks went by the participants could even taste 0.07g/L of MSG per 1L of soup. The average threshold for the whole group was +/-0.25g/L. It has also been indicated that 'Added MSG' label on food packaging can have an influence on 'consumers' perception about that food. In order to understand the consumer perception of MSG, the sensory attributes and the consumer acceptability of five commercially available tomato soup samples along with four other soup samples containing varying amount of MSG prepared in the laboratory were studied and a 9- point hedonic rating test was used. A total of 50 participants were invited to take part in this study. Samples were presented in random order and individual participants evaluated the overall liking of the soup samples as well as attributes such as colour, texture and the savouriness of the soup. Overall, the results show that samples containing MSG has a strong savoury taste as compared to soups without MSG. These samples also were preferred by most of the participants. Gas chromatography-mass spectrometry study was conducted to identify the levels of added MSG in commercial soup samples. Maggie, Continental, Home Brands, Watties and Campbell were purchased from supermarkets for analysis. Maggie soup packaging identified on the packaging as added flavour enhancer 621(MSG), but the other manufacturers claimed as no added flavours. After analysis it was observed that the apart from Maggie, other soup samples also contained traces of MSG, thus indicating the presence of compounds in minute amounts.