Author(s):
Ribeiro, Clara 
; Vicente, A. A. ; Teixeira, J. A. ; Miranda, Cândida
Date: 2005
Persistent ID: http://hdl.handle.net/1822/3684
Origin: RepositóriUM - Universidade do Minho
Subject(s): Edible coatings; Strawberry shelf-life; Oxygen permeability; Wettability of edible coatings
Description
The objectives of this work were to study the ability of starch, carrageenan and chitosan
based coatings to extend the shelf life of strawberry fruit (Fragaria ananassa). To do so,
the surface properties of fresh strawberry and the wettability of the coatings were studied.
The superficial tension of the strawberry was 28.94 mN/m, and its polar and dispersive
component was 22.99 mN/m and 5.95 mN/m, respectively. The critical superficial tension
of the strawberry was 18.84 mN/m, obtained from a Zisman plot.
The wettability of the coatings (starch, carrageenan and chitosan) is optimized with
compositions of, respectively: 2 % of starch and 2 % of sorbitol; 0,3 % of carrageenan,
0,75 % of glicerol and 0,02 % of Tween 80; 1 % of chitosan and 0,1 % of Tween 80.
The effect of the application of these coatings in fresh strawberry was assessed by
controlling the content in soluble solids, the colour evolution, the firmness, the mass
variation and the microbiological growth during a period of 6 days. No significant
differences were found between the chromaticity coordinates. The minimum loss of
firmness was obtained in strawberries coated with carrageenan and calcium chloride. The
minimum loss of mass was obtained in fruits with chitosan and carrageenan coatings both
with calcium chloride. Relatively to the content in soluble solids the coating of chitosan and
calcium chloride presented the best result.
The addition of 1 % of di-hydrated calcium chloride to coatings was also studied, and
this was shown to decrease the microbial growth rate of the fruit. The minimum rate of
microbial growth was obtained with strawberries coated with chitosan and calcium
chloride.
