Effect of package light transmittance on vitamin content of milk. Part 2: UHT whole milk

Abstract

This work is the second part of a milk study evaluating the effect of package light transmittance on the vitamin content of milk, in this case on UHT whole milk. The milk was stored at three different light intensities in polyethylene terephthalate (PET) bottles with varying light transmittance as described by Saffert et al. (2006). Changes in the vitamin A, B 2 and D 3 content were monitored over a storage period of 12 weeks at 23°C. Losses in vitamins A and B 2 were most pronounced in completely transparent PET bottles exposed to the highest light intensity. In these bottles, a reduction of the light intensity reduced the vitamin A loss from 88 to 66%, while in the case of vitamin B 2 the complete decomposition was just delayed from 4 to 8 weeks storage. The vitamin D 3 losses in clear PET bottles were almost independent of the light intensity. For pigmented PET bottles, the impact of package light transmittance and light intensity differed for each vitamin. An increase in package light transmittance and light intensity was found to be most decisive for vitamin B 2 stability. In the case of vitamin D 3 , only the increase in light intensity was found to be of relevance, whereas for vitamin A stability the influence of increased package light transmittance and light intensity could not be clearly observed. In dark-stored 'control' samples, the analysed vitamins were almost stable.

Effect of package light transmittance on the vitamin content of milk, part 3: Fortified UHT low‐fat milk

“…In the dark-stored 'control' sample, the initial vitamin D 3 content was almost completely retained. When comparing the present results with those obtained for UHT whole milk, 16 signifi cantly higher losses could also be found for vitamin D 3 but only in the case of the clear PET bottles, which again demonstrates the more destructive effect of light on the added fat-soluble vitamins.…”

“…When comparing the present results with those obtained for UHT whole milk, 16 signifi cantly higher vitamin A losses could be observed in the fortifi ed milk especially for the clear and lowest pigmented PET bottles as illustrated in Figure 3. This result Table 1…”

“…Summarizing the present fi ndings on the impact of package light transmittance on the vitamin content of fortifi ed UHT low-fat milk and those obtained for UHT whole milk 16 and pasteurized whole milk, 15 it can be stated that packages without any light barrier properties like clear PET bottles are insuffi cient to protect the milk vitamins A, B 2 and D 3 under commercially relevant storage conditions independent of the milk type. Due to the comparatively short storability of pasteurized milk, already the use of low-pigmented PET bottles (PET variant 2) led to a signifi cant improvement so that after a 10 day light-exposure period, more than 80% of the initial vitamin A and B 2 levels were retained.…”

“…Due to the comparatively short storability of pasteurized milk, already the use of low-pigmented PET bottles (PET variant 2) led to a signifi cant improvement so that after a 10 day light-exposure period, more than 80% of the initial vitamin A and B 2 levels were retained. 15 In the case of fortifi ed UHT low-fat milk and UHT whole milk, 16 higher pigmentation levels were necessary to obtain comparable vitamin retentions of at least 80% after a quite realistic light-exposure period of 4 weeks under commercially relevant storage conditions. After a prolonged storage period of 12 weeks, however, even the high-pigmented PET bottles could not prevent signifi cant losses in vitamin A (70%) in fortifi ed UHT low-fat milk due to the more destructive effect of light on added vitamin A when compared with naturally occurring vitamin A.…”

“…Vitamin A retention in fortifi ed UHT low-fat milk and UHT whole milk16 packed in PET bottles during a 12week storage period at 23°C and a light intensity of 700 lux. PET variant 1 -fortifi ed milk (᭜), PET variant 1* -whole milk (᭛), PET variant 2 -fortifi ed milk (),PET variant 2* -whole milk (ٗ).…”