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Pré-congélation des végétaux par immersion.

Author(s) : LANOISELLÉ J. L., TOUMI S., CLAUSSE D.

Type of article: Article

Summary

A new immersion-mechanical freezing process of vegetables is presented: the material under investigation was first exposed to immersion freezing in a NaCI solution and then freezing was completed through mechanical refrigeration (blast air freezing). The process was developed with green beans. After blanching and cooling, beans were immerged at - 16°C for less than one minute in a 22% w/ w NaCI solution. During immersion freezing a thin ice layer was then formed in the surface of the product, which reduced water loss during air-blast freezing. As the time of contact with brine was rather short, uptake of solute (NaCl) by the foodstuff was limited < 0.6%). The whole process has five main advantages: fast, energy saving, higher quality end product (texture improvement), individual pieces freezing (IQF) and reduction of dehydration losses. Theses advantages resulted from very fast initial freezing step performed in the brine solution. Heat transfer coefficients were measured with heat flux sensors with minimum agitation of the solution. The obtained coefficients (300 Wm-2.°C-1 to 700 Wm-2.°C-1) were 15 to 20 times higher in the liquid medium than in the air-blast tunnel with an air temperature at -35°C and an air velocity of 2 m·s-1. The total residence time of food in the combined immersion-mechanical freezing process to obtain a care product temperature of -18°C (O°F) was 2 minutes compared to 6 to 8 minutes for an air-blast tunnel freezing process. After thawing and cooking in water, no salty taste was detected by consumers and the texture quality was improved and comparable to cryogenic frozen beans.

Details

  • Original title: Pré-congélation des végétaux par immersion.
  • Record ID : 30013833
  • Languages: French
  • Subject: Technology
  • Source: Revue générale du Froid & du Conditionnement d'air - vol. 103 - n. 1147/1148
  • Publication date: 2014/10

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