Theoretical and experimental study on cryogenic freezing of berries

This paper presents some aspects concerning raspberries and blueberries freezing using liquid nitrogen: duration of the process, microscopic analysis of frozen and thawed berries, parameters variation along the freezing tunnel, advantages and disadvantages of this modem method. Quick freezing of food products in a cryogenic freezer consist in the use latent heat of evaporation of the liquid nitrogen, as well as of the sensible heat of the vapors, whose temperature increase up to final temperature of the frozen product. Considering the demands for reduction of fuel consumption involved in generation of electrical energy needed for classical refrigeration systems, this method uses for freezing liquid nitrogen obtained as secondary product at oxygen production.