Standard Melanoidin

The glass transition temperature 7 g of melanoidins has been considered by Anese et alS6 The freeze-dried Solution A and the Standard Melanoidin showed 7 g of 30 and... 

C, respectively, compared with those of glucose, glycine, sucrose, maltose, and starch, 31, -71, 62, 87, and > 200 °C, respectively. Mixing the Standard Melanoidin with water rapidly reduced the Tg for 4.4% (w/w, total) water rg=19°C and for 18.3% water Tg = -70 °C. The DSC thermogram also showed sharp endotherm peaks for Solution A and the Standard Melanoidin at 160 and 140 °C, respectively, attributed to the degradation of carbonyl compounds. The temperature at which this peak occurs was also lowered on addition of water 4.4% lowered it to 100 and 24% to 80 °C. 

The thermal degradation of standard glucose-glycine melanoidins has been extensively studied by Tehrani el alF After heating for 2 h at 125 °C, there was a weight loss of 32%. The water-insolubles (5 g from the equimolar mixture 9 3.75 g originally) and the non-dialysables (119 mg) were heat-treated, either (A) successively at 100,150,200, and 220 °C or (B) as a fresh sample at each temperature and at 250 and 300 °C. Heat-treatment A produced about 10 times the amount of volatiles from the non-dialysables than from the insolubles. This was seen for 5-methylfurfural, furfural, 2-acetylfuran,... 

Wagner et a/.488 examined four fractions from the standard glu-Gly reaction Solution A, LMM melanoidin and high-molecular-mass (HMM) melanoidin (12.4 kDa... 

T. Hofmann, On the preparation of glucose/glycine standard melanoidins and their separation by using dialysis, ultrafiltration and gel permeation chromatography, in Melanoidins in Food and Health, Vol. 2, J. M. Ames (ed), European Communities, Luxembourg, 2001, 11-21. 

Our interest in the analysis of nonvolatiles, thus, may involve taste substances or substances that indirectly influence taste or aroma. As mentioned earlier, in the first case, we are interested in the analysis of substances that impart sweetness, tartness, bitterness, saltiness, or unmami sensations. The analysis of these substances is reasonably well defined. In the latter case, the analyses employed are less well defined and are unique to the components one wishes to analyze. For example, we may wish to measure substances (e.g., melanoidins) that interact with sulfur aroma compounds (in coffee). There are no standardized methods for the analysis of melanoidins in foods and thus, the protocols have to be developed. In this chapter, we will only briefly discuss the established methods for the analysis of taste substances. Due to the specificity of methods for the analysis of nonvolatiles that may indirectly influence flavor perception, we will only refer the reader to the literature [93-100]. 

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