| Summary: | As a healthy alternative to traditional oil-fried potato chips, microwaving potato slices
under vacuum simulates puffing by deep-frying without the presence of oil. The main objective
in this study was to determine how potato cultivar and post-harvest storage affected the quality
of vacuum microwave-dried (VMD) potato chips, and to identify cultivars suitable for VMD
chip processing.
Potato tubers from eighteen cultivars, harvested in 1998, were stored for (1) six months
at 12°C; and (2) ten months at 4°C with reconditioning at 12°C for 2 weeks prior to VMD chip
processing. VMD chip quality, in terms of texture (sensory and instrumental methods) and
colour was evaluated. Observations of tuber specific gravity and moisture content were taken
immediately prior to VMD chip processing.
In 1999-2000, tubers from six commercially important cultivars (Kennebec, Shepody,
Russet Burbank, Norland, Warba, and White Rose) were stored at 4°C for 5 to 10 months
followed by reconditioning at 12°C for 2 weeks prior to VMD chip processing. Monthly
observations of VMD chip texture, tuber specific gravity and moisture, starch, amylose,
reducing sugar and soluble carbohydrate contents were taken. Potato slices were dehydrated
using three methods (air drying, freeze drying, and vacuum microwave drying) and the
structural characteristics examined by scanning electron microscopy. VMD chips were
rehydrated (at 100°C and 25°C) and their moisture absorption rates determined.
Specific gravity and starch content highly correlated with VMD chip sensory crispiness
and instrumental peak force values. Cultivars with low dry matter content (Norland, Warba,
and White Rose) produce chips that required less force for fracturing, compared to cultivars
high in dry matter content (Kennebec, Shepody, and Russet Burbank). Tuber physiology
appeared in part to influence VMD chip puffing. Cultivars with low dry matter content
produced chips with greater tissue porosity and/or expansion. From rehydration experiments,
the rapid moisture absorption in cultivars with low dry matter content suggested a less dense
chip tissue structure.
Changes in tuber specific gravity and moisture content during storage affected VMD
chip quality. Tuber specific gravity, starch and moisture contents, and VMD chip peak force
values did not significantly change over time when tubers were stored from 5 to 10 months at
4°C with reconditioning at 12°C for 2 weeks. However, tuber reducing sugar content did
significantly increase during this storage treatment. Neither cultivar nor storage was found to
significantly affect VMD chip Hunter L values.
Cultivars Norland, Warba, and White Rose (which are unsuitable for oil-fried chip
production due to high sugar content) may be well suited for VMD chip production. From these
cultivars, VMD chips of consistent quality were produced from tubers stored for up to 10
months.
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