There is no significant loss of dietary fiber when grapes are processed into raisins.

The process of making raisins from grapes does result in some loss of nutrients, but the overall nutritional value is not seriously affected. The water in the raisins is evaporated, leaving some of the nutrients in the grapes relatively concentrated. It is worth noting that sun-dried raisins suffer a significant loss of vitamin C, which is susceptible to inactivity due to heat and oxidation. Grapes do not lose significant amounts of dietary fiber when processed into raisins.

Phenolics and antioxidant activity of raisinsThe polyphenols (polyphenol), phenolic acid, and tannins in grapes are often collectively referred to as PPTs.Williamson's demonstrated that the most abundant PPTs in raisins are flavonols, quercetin, kaempferol, and phenolic acid, caffeoyltartaric acid ( caftaric acid) and coumaroyl tartaric acid (coutaric acid). On a wet weight basis, raisins contained higher levels of PPT phenolic acids such as protocatechuic acid and oxidized cinnamic acid than grapes.

Precautions for processing grapes into raisins

When it comes to the selection of raw materials, it's all about being selective. The grapes selected should have thin skins, while the flesh needs to be relatively soft and not broken in appearance. It is best to choose varieties with a high sugar content, such as the coreless white as well as rose-scented. When choosing, you should pick ripe grapes, and after purchasing the grapes, you need to reduce the bunch.

Large bunches should be divided into smaller bunches to prevent them from hanging on the wall for a long time and falling to the ground when drying. Wash the prepared ones in lye water to shorten the finishing time. Then you can put the grapes on the sun plate for sun exposure, and need to be turned, so that the surface of the grapes are heated evenly.

Reference: Baidu Encyclopedia - Raisins