Temperature dependence ascorbic acid stability

The color of anthocyanins containing media depends on different factors. The most important are structure and concentration of anthocyanin pigments, pH, and presence of copigments and metallic ions, all of which influence the color shade. Also important are the temperature and presence of oxygen, phenoloxidase, ascorbic acid, and sulfur dioxide, all of which influence the anthocyanins degradation rate and color stability. 

The stability of vitamin B12 is very dependent on a number of conditions. It is fairly stable at pH 4-6, even at high temperatures. In alkaline media or in the presence of reducing agents, such as ascorbic acid or SO2, the vitamin is destroyed to a greater extent. 

The effects of pH in the oxidative destruction of folates has been reviewed by several authors (6,10,28). Each vitamer has its own unique pH stability, and it is therefore sometimes difficult to optimize extraction conditions for all folate forms in a single extraction. The pH of the extractant, presence of oxygen, the temperature used, and in addition, buffer type, can all affect the efficiency of folate extraction (8). Several folate derivatives can be altered during extraction. The presence of phosphate accelerates conversion of 10-HCO-H4-folate to (1) 5,10-CH+-H4-folate and (2) 5-HCO-H4-folate at pH values below pH 7 during extraction. Also, 5,10-CH2-H4 folates can be converted to H4 folate during extraction (29). As the use of ascorbic acid reduces 5-CH3-H2-folate to 5-CH3-H4-folate, the former can be quantified only in the 5-CH3-H4-folate pool (30). Thus, extraction conditions can affect the vitamer distribution and therefore need always to be carefully considered and fully reported. The chosen extraction conditions are dependent on the purpose of the analysis to be carried out. 

If fresh products are held at the appropriate temperature and consumed in a short period of time, they have more vitamin C than commercially canned products. Vitamin C degrades rapidly after harvest and its amount depends on the commodity, temperature, pH and other factors. During storage (and processing), the stability of ascorbic acid is higher in fruits that have lower pH than vegetables. For example, the effect of storage on the vitamin C content in... 

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