Effects of liquid nitrogen pretreatment on the osmotic dehydration and quality of cryogenically frozen blueberries (Vaccinium angustifolium Ait.)

Blueberries are a widely consumed fruit known for their high antioxidant content. Due to their short shelf life at refrigerated temperatures, they can be frozen or dried to overcome perishability limitations. Liquid nitrogen pretreatment may be able to increase the permeability of blueberries' skin, thereby amplifying the effects of osmotic dehydration through increased transfer of moisture and solids. This study evaluated the effects of liquid nitrogen pretreatment on osmotic dehydration and the resulting physicochemical properties of cryogenically frozen blueberries. Blueberries were immersed in liquid nitrogen (− 196 °C) for 10 s and then thawed. Pretreated and un-pretreated samples were placed in a 60°Brix sucrose solution (40 °C) for 8 h, followed by cryogenic freezing. Liquid nitrogen pretreated blueberries experienced greater moisture loss and solids gain than un-pretreated samples after osmotic dehydration, while having similar anthocyanin and total phenolic contents. This study demonstrated that liquid nitrogen pretreatment facilitates water and sugar diffusion in blueberries during osmotic dehydration while maintaining nutritional quality.