Environmentally Friendly Method for Freezing Raspberries and Blueberries Using Liquid Nitrogen

Abstract

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. The resulted nitrogen gas is discharged in the environment, and, being chemically inert, it does not contribute to harmful chemical components generation. This paper presents some aspects concerning raspberries and blueberries freezing using liquid nitrogen: duration of the process, freezing capacity, advantages and disadvantages of this modern method. Quick freezing of food products in a cryogenic freezer consist in the use of the 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. The use of cryogenic freezing with liquid nitrogen and carbon-dioxide is regarded as the "century's revolution" in the food area.

Numerical Analysis of a Liquid Nitrogen (LN2) Engine for Efficient Energy Conversion

“…LN 2 is used in various industries due to its very low temperature, low reactivity, and as being an energy carrier . LN 2 is used for freezing, preserving, and transporting food products. , It is also used for cryosurgery and cryotherapy for skin treatments such as removal of abnormal skin growth, such as warts. Some other uses include quick freezing of water pipes to work on them, branding cattle, cooling materials for machining, etc.…”

Researches on the freezing of blueberries and green bean pods using an experimental model of a fast freezing equipment

“…The conditions that vegetables and fruits have to fulfill to be preserved by freezing are determined by: compatibility with freezing preservation, widespread acceptance by consumers, high technological yields, virus resistance, mold, physiological defects and insects, uniformity of maturation, good handling resistance, pronounced color and flavor, firm texture with as little as possible deformation and softening tendency to thaw, as little juice as possible in defrosting. One of the modern freezing techniques is that of cryogenic freezing using liquid nitrogen (N2) as a cooling substance [11,13,14]. Compared to conventional freezing techniques, the cryogenic method has the following advantages: rapid freezing, inhibition of bacterial growth, limited dehydration, considerable reduction of quantitative losses, optimal nutritional preservation, maintenance of the appearance and taste of the food.…”