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Studies on the development of rancidity in stored flour of pearl millet [Pennisetum glaucum (L.) R. Br.]

KrishiKosh

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Title Studies on the development of rancidity in stored flour of pearl millet [Pennisetum glaucum (L.) R. Br.]
 
Creator Sharma, Amit
 
Contributor Saharan, M.R.
 
Subject Bajra, Pearl millet, Peroxidase, Phenols, Rancidity, Storage
 
Description The investigation was carried out on two pearl millet hybrids viz., HHB 94
and ICMA 94222A x 78/711. The former is grey in colour and has high fat and
phenols content and possesses high activity of peroxidase. Light yellow hybrid
ICMA 94222A x 78/711 also has high fat content and possesses comparatively low
total phenols content as well as low activity of peroxidase. Composition of flour
of both hybrids was modified by differential extraction of fat and phenols. Type I
and type II flour containing 40 and 60% lesser fat content (compared to control
flour) whereas type III and type IV flour containing 40 and 60% lesser phenols
respectively were prepared. The unmodified or modified flour was stored at 37oC
at ambient relative humidity for 0, 4 or 8 days in a BOD incubator. Defatting of
flour caused an increase in fat acidity ‘FA’ and free fatty acids ‘FFAs’ but showed
no effect on peroxide value ‘PV’ of the flour. On the other hand, extraction of
phenols decreased FA, FFAs and PV of flour of both hybrids. Values of rancidity
indicators viz., FA, FFAs and PV of control as well as modified flour (all the
types) of both hybrids increased with increasing storage time. FA and FFAs in
flour of both the hybrids having lesser phenol content increased much faster than
that had correspondingly lesser fat content. Despite a higher rate of increase, by
8th day of storage, FA and FFAs of type II and type IV flour was much less than
that of type I and type II flour. There was no effect of reducing fat content of fresh
flour of either of the hybrids on content of total phenols and on level of
peroxidase activity. On the other hand, extraction of phenolics showed a profound
inactivating effect on the enzyme activity of both the hybrids. In control flour of
HHB 94 and ICMA 94222 x 78/711, very strong and strong rancid odour was
detected on 8th day of storage. Removal of phenolics from flour of both the
hybrids before storage reduced the intensity of off-odour developed during storage
of flour. Blanching treatment was very effective for inactivating peroxidase in
grains. Blanching of grains of HHB 94 for 120 seconds almost completely
inactivated peroxidase. FA, FFAs and PV of fresh flour produced from grains
blanched for 90 and 120 seconds was lower than that produced from untreated
grains. Upon storage, FA, FFAs and PV of control flour increased with increasing
time of storage whereas in flour produced from grains blanched for 120 seconds
the values of these rancidity indicators virtually did not change further. Flour
produced from blanched grains (type V, type VI and type VII) had lesser total
phenols content than that of control flour. There was no change in the content of
total phenols of lour prepared from untreated as well as treated grains upon
storage. Based on results of both the experiments, it was concluded that high
content of total phenols and high activity of peroxidase are responsible for
generating rancid odour in stored flour rather fat content of grains.
 
Date 2016-11-23T14:19:30Z
2016-11-23T14:19:30Z
2006
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/87247
 
Language en
 
Format application/pdf
 
Publisher CCSHAU