A comparative study of raspberry dehydration by lyophilisation or conventional drying

Year 2018, Volume: 2 Issue: 3, 267 - 272, 15.12.2018

Otília Gonçalves Marco Alves Joana Grácio Valentim Nunes

Abstract

Dehydration
is a food preservation process that allows to increase the availability of
products on the market, as well as the introduction of new products. The
objective of this work was to perform a comparative study of processes of
dehydration of raspberry by freeze-drying (lyophilisation) or conventional
drying. Raspberry is a perishable fruit, with about 85% (w/w) water content,
and there is a need for preservation processes that generate new products with
long term availability. Raw materials were subjected, or not, to blanching
pre-treatments. It was analysed the effect of these treatments on physical
parameters, such as water activity, colour and moisture content as well in the
drying kinetics. It was found that conventional drying allowed to reduce water
content to 20.7 to 35.8% while lyophilisation permitted to achieve values from
11.6 to 14%. It was also observed that lyophilisation process correspond to
higher colour difference indexes, ranging from 5.30 to 11.8 values.

Keywords

Blanching, Drying kinetics, Lyophilisation, Raspberry

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