Folate concentrations in rosehips and commercial rosehip products and factors affecting folate retention during drying were investigated. On the basis of the raw material studied during 3 years, rosehips were shown to be a rich folate source, 400-600 microg/100 g based on dry matter and 160-185 microg/100 g based on the fresh weight (edible part). Rosehips are not often consumed fresh; therefore, drying to produce stable semimanufactures is a crucial step. The degradation of folate was shown to be dependent on the drying time until the water activity was below 0.75. The required drying time was reduced by cutting the rosehips in slices and to some extent also by increasing the temperature. Retention of folate and ascorbic acid was affected by the same factors, and high content of ascorbic acid could provide a possible protection for folate degradation.

The possibility of predicting the shelf-life of pasteurized carrot juice by isothermal microcalorimetry or change in pH was investigated and compared with traditional plate count results. A small increase in thermal power (2 µW), maximal increase of and acceleration of thermal power all gave rapid, well-correlated results for the shelf-life, as did pH, during accelerated storage. The effect of accelerated storage (17 • C) on the microbial flora of pasteurized carrot juice was also compared with the flora from storage at 8 • C, and it was found that accelerated storage is feasible for the rapid evaluation of shelf-life, but that the microbial flora in the spoilt juice will be different.

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