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Effect of electric field and osmotic pre-treatments on quality of apples after freezing–thawing

Parniakov, O., Lebovka, N.I., Bals, O., Vorobiev, E.
Innovative food science & emerging technologies 2015 v.29 pp. 23-30
apples, aqueous solutions, color, electric field, freeze-thaw cycles, freezing, glycerol, ohmic heating, osmotic treatment, pulsed electric fields, texture, thawing
This work discusses the effects of pulsed electric field (PEF), ohmic heating (OH), and osmotic (O) treatments on the structure of apple tissue and its freezing/thawing behaviour. Apple discs were treated at electric field strength E=800V/cm (PEF, isothermal regime) and E=40V/cm (OH, non-isothermal regime) to a high level of tissue disintegration (conductivity disintegration index Z was ≈0.98) and then were subjected to osmotic (O) treatment in the aqueous solution of glycerol (20wt.%). The distribution of osmotic solution was practically homogeneous inside the disc of PEF-treated tissue and highly inhomogeneous in untreated and OH-treated samples. The freezing–thawing (FT) experiments (+20°C→−40°C→+20°C) were done in order to reveal the effects of combined modes of treatment on the structure of apple tissue. The most pronounced reducing of both freezing and thawing times and strengthening of the apple texture were observed for PEF treatment.Freezing-assisted preservation of plant materials in the most natural-looking state with near-original texture and colours requires thorough optimization of freezing operation. In this study, the research of the impact of pulsed electrotechnologies combined with osmotic pre-treatment on the structure of apple tissue, its freezing/thawing behaviour and texture quality, is provided.