Biomedical Engineering Reference
In-Depth Information
germination after storage for 12 months, but moisture content of the grain was not
given.
98
Generally, low O
2
or high CO
2
atmospheres have no negative effects on
viability of dry grain and both low O
2
(<0.5%) and high CO
2
(>50%) help preserve
the germination of wet grain.
57
Nutrient Changes in Grain
A controlled atmosphere of 97 to 98% N
2
, 1 to 2% CO
2
, and 1% O
2
slows hydrolytic
processes in the lipids of rice grain compared to grain stored in air.
99
Pure N
2
atmospheres at 20°C stabilize protein and amino acids and the cooking properties
of rice at 18.4 and 23.2% MC compared to storage in air.
100
Elevated N
2
, with
negligible O
2
, retain higher gluten quality in stored wheat than storage in air
101
and
the milling and baking properties of wheat are maintained longer than in air even
at high moisture contents.
102
An anoxic environment (N
2
) slows the oxidative activity
and better preserves the organoleptic properties of grains and even hazelnuts.
103
Storing dry grain under airtight conditions (15 to 25% CO
2
for several months)
maintained its quality
104
but wet grain (>16% MC) was tainted with fermentation
odors, was discolored, and was unsuitable for bread-making (after 2 months at 21%
MC). At high moisture, there was an increase in reducing and a decrease in non-
reducing sugars.
105
After storing wheat for 3 to 4 years under vacuum, CO
2
, or N
2
,
Stopczyk
107
concluded that changes to sugars depended mainly on moisture and
temperature rather than on gas concentrations. Starch viscosity decreased more in
air storage than in CO
2
storage. Munzing
107
indicated that flour from 20% MC wheat
stored for 6 months under CO
2
led to reduced loaf volume in 6 months and that an
N
2
atmosphere (negligible O
2
) was preferable for long-term storage of wet wheat.
Dry wheat stored for 18 years at low O
2
had no decrease in loaf volume.
108
Wet
rapeseed or sunflower seed (13 to 15% MC) stored under airtight conditions pro-
duced off-odors due to microbial fermentation but the production of free fatty acids
was slower than when stored in air.
109
Effect of CA on Fungi and Mycotoxins Production
Elevated CO
2
(20 to 60%) inhibits fungi and the production of mycotoxins by fungi
in stored grain
110
including T-2 toxin,
111
patulin,
112
ochratoxins,
113
penicillic acid,
114
and aflatoxin.
115
The prevention of aflatoxin production in wet corn is of considerable
importance in animal feed grain.
116
Reduction of O
2
is less effective in preventing
mycotoxins than the elevation of CO
2.
117
In dry grain, 20% CO
2
inhibits microflora; in wet grain 80% CO
2
is needed.
Some species of
Fusarium
,
Aspergillus
, and
Mucor
are tolerant to high CO
2
levels.
117
In wet grain, at 1 to 2% O
2
and 15 to 40% CO
2
, typical microflora were the yeasts
Hansenula
and
Candida
(60 to 80% RH) followed by anaerobic fermentation caused
by lactic acid bacteria and yeasts (>90% RH). Filamentous fungi gradually disappear
during storage.
105
Fungi do not grow at <1% O
2
.
118
Yeasts can survive at <0.5% O
2
.
Richard-Molard et al.
119
found that corn stored at 21% MC in hermetic storage
produced a CO
2
atmosphere with 0.5% O
2
in 4 to 5 days and there was a slight
Search WWH ::
Custom Search