Vitamins thermal decomposition

To compare the performance of the three yeast species and to prevent growth limitations due to any nutritional deficiency, the BSG hydrolyzate was supplemented with several mineral nutrients and vitamins to reach the concentrations described in Duarte et al. [17], D. hansenii biomass production for subsequent studies was carried out using a previously optimized medium containing 0.5 g F KH2PO4 as the only supplement to BSG hydrolyzate [2]. To prevent nutrient thermal decomposition, all media were filter sterilized using a 0.22-pm Gelman membrane filters (Pall Corporation, Arm Arbor, MI, USA). 

Vitamin C and Ion attachment mass spectrometry with a temperature-pro-grarmned direct probe allows the detection of irrtact pyrolysis products. It, therefore, offers the opportunity to monitor directly thermal byproducts on a real-time basis and potentially to detect thermally imstable products. EGA-IAMS is used to study the real-time, non-isothermal decomposition of vitamin C [30]. The results were compared with those obtained in a similar study on thermal decomposition of vitamin C using pyrolysis GC/MS. Significant differences were found between the two techniques, in terms of the nature and relative amoimts of products formed. A major difference between the two techniques was in the transportation time of the pyrolysis products out of the pyrolysis chamber (or hot zone). The time was significantly shorter in EGA-IAMS than in pyrolysis GC/MS, which reduces the occmrcnce of secondary reactions of the primary pyrolysis products. Some decomposition products formed in the EGA-IAMS system were not detected in the previous pyrolysis GC/MS study [38] and thus were detected for the first time. For instance, dehydro-L-ascorbic acid was observed as a decomposition product. This compoimd was the main degradation product detected by means of EGA-IAMS. While it is an important compoimd because it possesses some biological activity, dehydro-L-ascotbic acid is difficult to measure due to its chemical instabihty. 

Juhasz M, Kitahara Y Fujii T. Thermal decomposition of vitamin C an evolved gas analysis-ion attachment mass spectrometry study. Food Chem. 2011 129 546-50. 

Liquid chromatography (LC) has become a useful tool in food analysis to ascertain food quality, to implement regulatory enforcement, or to comply with national and international food standards. LC is chosen for multiple applications because it can be applied to a wide range of different samples, allows separation of compounds ranging from ions to biopolymers, and employs mild separation conditions, such as low temperature, thus precluding the thermal decomposition of unstable compounds, such as vitamins or pol)q)henols. LC also provides good sensitivity, resolution, and selectivity. 

Figure 2.6 Decomposition curves corresponding to 100 kGy electron bean irradiated UHMWPE and subsequent stabilized thermally by annealing (plOOA), remelting (piOOR), or by diffusion of vitamin E (plOOVE). Adapted from Ref. [76].

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