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Effect of high-temperature short-time pressure blanching on physical, chemical and sensory properties of frozen cornLatham, Debra L. 14 December 1987 (has links)
The effect of HTST pressure blanching processing parameters, as
compared to conventional steam blanching, on enzyme activity,
moisture, drip loss, shear force, sensory attributes and consumer
acceptability of frozen sweet corn were determined. Complete
inactivation of catalase and peroxidase required HTST treatments of
60 psi and 75 psi, respectively. No lipoxygenase activity was
detected in the blanched corn. Moisture content increased slightly
and maximum shear force decreased in the HTST blanched corn as
compared to the steam blanched samples. No differences were observed
in total work of compression and shear or drip losses in frozen corn
prepared by the two blanching processes. Blanch pressures of 60 psi
and 75 psi resulted in corn equivalent in sensory qualities to the
control steam blanched product as judged by a trained panel. The 30
psi blanch treatment was rated higher in stale/oxidized, fishy,
bitter, and other undesirable descriptors. Stale/oxidized and sweet/caramel character increased with storage time. Consumer tests
resulted in no significant differences in acceptability across blanch
treatments or storage time. / Graduation date: 1988
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A study of some factors affecting the quality of frozen corn-on-the-cob /Beale, William Leon January 1958 (has links)
No description available.
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Effects of maturity and blanching on carbohydrate components of frozen normal sweet (su) and supersweet (sh₂) cornSu, Shanghe 04 October 1989 (has links)
Three varieties of sweet corn (Zea mays L.) , including
two supersweet (Crisp 'N Sweet 710 and Rogers 3376) and one
normal sweet (Jubilee), were harvested at six stages of
maturity (80-72% moisture for supersweet and 75-68% moisture
for normal sweet) at three days intervals. Changes in
physical and chemical properties over the 15 day harvest
period and effects of steam blanching on carbohydrate
composition of both genotypes of sweet corn were determined.
Moisture content of the kernels decreased with
maturity. A quick microwave oven moisture method for
determining moisture content of normal sweet and supersweet
corn was evaluated and found to be a good alternative method
for the time-consuming standard AOAC vacuum oven method.
Yield (as represented by average ear weight) increased
linearly with maturity. Percent soluble solids was determined to be a satisfactory maturity index for normal
sweet corn but not for supersweet corn. The pericarp
content in the normal sweet corn Jubilee increased 25% over
the 15-day harvest period compared to a mean of 5-6% in the
supersweet varieties. Values of the shear press tests were
not significantly correlated to % moisture, and only values
of compression work showed a positive trend to increase with
maturity.
Total sugars of supersweet corn averaged 2-3 times
higher and decreased more slowly than those of normal sweet
corn in the comparable maturity range for processing.
Sucrose was the major sugar in both corn genotypes and
represented about 80% of the total sugars (9-20% dry weight)
in normal sweet corn versus 90% of the total sugars (30-45%)
in supersweet corn. Polysaccharides consisted mainly of
starch in supersweet corn and of water soluble
polysaccharide (WSP) in normal sweet corn. Normal sweet
corn contained about twice as much polysaccharides as did
supersweet corn. Percent total polysaccharides increased
with maturity. Although higher in sugars, supersweet corn
had lower % total carbohydrates than normal sweet corn due
to its low polysaccharide content.
Blanching of corn-on-the-cob for 10 minutes in 99°C
steam resulted in a significant loss of sugars. Blanching
did not significantly reduce total polysaccharides of sweet
corn. / Graduation date: 1990
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Peroxidase and lipoxygenase activities and their effect on the stability of polyunsaturated fatty acids in two different varieties of sweet corn (Zea mays L.), Jubilee and GH 2684, during frozen storageRodriguez-Saona, Luis Enrique 01 October 1993 (has links)
The effect of different blanching treatments and
packaging materials on the enzymatic (lipoxygenase and
peroxidase) activity and fatty acid stability of two
different varieties of sweet corn on the cob (Jubilee and GH
2684) was evaluated during nine months of frozen storage at
-23.3°C.
The initial moisture content in the kernels of the two
sweet corn varieties averaged 72.5%. After nine months of
frozen storage the moisture content in the kernels of corn
depended greatly on the packaging material used. The ears
stored in Cryovac B and E bags showed the best moisture
retention (72.2% final moisture content), followed by the
polyethylene bags (71.4%) while the ears stored without
packaging material showed severe dehydration (70.1%).
The peroxidase and lipoxygenase activities were
determined using spectrophotometric assays on a crude
extract obtained from liquid nitrogen powdered corn. Both
unblanched varieties of sweet corn showed similar initial
peroxidase specific activity and general behavior during the
nine months of frozen storage. The presence of lipoxygenase
isozymes with different thermal stabilities in both
varieties was suggested by the higher lipoxygenase specific
activity found in Jubilee after freezing and nine months of
frozen storage (0.135 units/mg protein) compared with the GH
2684 variety (0.115 units/mg protein).
Complete inactivation of lipoxygenase was obtained
after 9 minutes steam blanching at 100°C. Peroxidase was
more heat resistant showing some remaining specific activity
after 9 minutes steam blanching with a complete inactivation
after 15 minutes steam blanching. No regeneration of either
enzyme was observed during the nine months of frozen storage
suggesting a permanent disruption of the active site of both
enzymes.
Relative fatty acid content was determined by gas
chromatographic analysis of fatty acids methyl esters. The
major fatty acids present in both varieties were palmitic
(14.93%), stearic (2.79%), oleic (31.54%), linoleic
(46.87%) and linolenic (1.89%) acids. Good stability of
the polyunsaturated fatty acids was observed during the nine
months storage at -23.3°C, with autoxidation as the main
mechanism responsible for the decrease in the relative percent of polyunsaturated fatty acids. Some enzymatic
oxidation also occurred, decreasing the linolenic acid
content.
The control of the degradation of polyunsaturated fatty
acids depended mostly on the frozen storage temperature
(-23.3°C) and not on the oxygen permeability of the different
packaging materials.
The results obtained in our study suggested that
blanching of the ears of sweet corn had an important effect
on reducing the enzyme activity but little effect on the
polyunsaturated fatty acid degradation after 9 months of
storage at -23.3°C. / Graduation date: 1994
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