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Freezing partially dried apples.

La congélation de pommes partiellement séchées.

Author(s) : BEN HAJ SAID L., BELLAGHA S., ALLAF K.

Type of article: Article

Summary

This preservation process comprises a drying process involving air convection followed by instantaneous controlled cooling (DIC) texturization/decontamination then freezing/deep freezing of the finished product. Optimization of these steps is performed by identifying the impact of the water content of apple samples on firmness following freezing. The water content of the apple samples examined prior to freezing ranges from 700% of the dry weight basis (bs) to 200, 166, 115, 64, 30% bs obtained using convection drying. Following optimized DIC treatment, the samples were frozen at a temperature of -30 °C, then thawed at a temperature of 4 °C. The results obtained demonstrate that following freezing/thawing, marked preservation of firmness was obtained with samples with a low water content (W<166% bs), whereas in the case of fresh apple samples and samples with a water content greater than 200% bs, marked loss of firmness occurred. Thus, the freezing of apples with a low water content exerts a negligible impact on the texture; the critical water content is thus between 200% and 166% bs. Freezing at a temperature of -30 °C was investigated using two different freezing rates. The impact of the water content was demonstrated in terms of i) the freezing duration, ii) the quantity of exuded water during thawing (EED), and iii) the texture (maximum penetration force - firmness index). The fastest freezing rate exerted a significant effect on samples with a high water content (700 and 200% bs). The freezing rate and the quantity of exuded water during thawing decreased considerably as the water content decreased. EED decreased from 12 g/100 9 of water initially present during the thawing of fresh frozen samples, and was less than 3 g/100 g of water for samples with a water content of 200% bs, even where the same freezing rate was applied. At the level of the texture, firmness was markedly improved where the water content of apple slices was low, and there was no significant effect on the freezing rate.

Details

  • Original title: La congélation de pommes partiellement séchées.
  • Record ID : 30021550
  • Languages: French
  • Source: Revue générale du Froid & du Conditionnement d'air - n.1160
  • Publication date: 2016/11

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