*5.8.1 Stability*

The stability of vitamin D throughout production and storage in dairy and milk products is verified, as well as its stability in high temperature short time handling and storage without light and acid [29].

Vitamin D loses its stability in some conditions. It decreases in acidic media as it transforms into its inactive form isotachysterol, or by heating to a temperature above 150°C in the presence of air [27]. However, it is stable at temperatures below zero, at 4–8°C, at 25°C, and during cooking at 200°C [24].

In the study of elevating vitamin D3 under two different conditions, high temperature processed decreased fat milks (increased temperature/decreased time, pasteurized at 73°C for 15 s, and ultra-heat treated, purified at 138°C for 2 s) and reduced fat yogurt (purified at a temperature of 85°C for a half hour), it is verified that the amount of vitamin D does not decrease during preparation [30]. In addition to that, it was stable during storage and has no effect on sensory qualities [23].

Banville found that vitamin D3 fortification in cheddar in the liposome form decreased after 3–5 months of maturing and lost its stability [21]. It is shown also that vitamin D3 has stability in nonfat foods such as in squeezed orange (storage for 30 days at 4°C) [31]. Both vitamin D3 and vitamin D2 showed their stability in fortified squeezed orange [32].
