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vol. 9, nr. 1 (2007)
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Effect of storage time on texture and selected properties of walnuts
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Agnieszka Kita1, Adam Figiel2
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1 Department of Food Storage and Technology, Wroc³aw University of Environmental and Life Sciences
ul. Norwida 25, 53-375 Wroc³aw |
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2 Institute of Agricultural Engineering, Wroc³aw University of Environmental and Life Sciences
ul. Che³mońskiego 37/41, 51-630 Wroc³aw |
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vol. 9 (2007), nr. 1,
pp. 69-78
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abstract:
The aim of this investigation was to determine the effect of storage time on selected properties of walnuts roasted according to different methods. The material for investigation consisted of halves of shelled walnuts roasted in hot oil (140oC/5 min.) and hot air (160oC/15 min.). The control samples were raw walnuts not subjected to thermal processing. Portions of walnuts, of 200 g mass, were vacuum packed in aluminium foil bags and stored in standard conditions for 5 months. In the samples, before storing and after each month of storage, the following parameters were determined: moisture content, texture - with the use of Instron 5544 apparatus, colour - using Minolta CR-200 colorimeter, as well as organoleptic features: colour, taste, flavour and texture according to 5-point scale (1-5 points). It was found that roasted walnuts were characterized by darker colour, lower moisture content and mechanical strength in comparison with raw walnuts. When in storage, there took place a slight increase in roasted walnuts moisture content and an insignificant decrease in raw walnuts moisture content. In the subsequent months of storage there could be recorded an increase in walnuts bending strength, while their compressive strength remained the same. The results of bending test were correlated with sensory assessment of nut texture. That double testing proved a loss of walnut crispness and an increase in their hardness. Roasting, especially that conducted in oil, caused worsening of walnut sensory properties in the course of storage. Disadvantageous alterations involved, first of all, increased hardness, as well as less favourable walnut taste and flavour.
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keywords:
walnuts, roasting, storage, texture, colour, sensory assessment
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original in:
English
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