α-amylase inhibitors in foodstuffs

Impact of partial replacement of rice with other selected cereals on idli batter fermentation and idli characteristics

Idli is a naturally fermented food, prepared using dehulled black gram dal and parboiled rice. In the first phase of the study, replacement of rice with some underutilized cereals like amaranth and finger millet was carried out at different proportions (25%, 50%, 75% and 100%, w/w) followed by sensory evaluation of the prepared idlis. Idlis prepared with 25% (w/w) replacement of rice with finger millet (25F) were more acceptable than idlis prepared with 25% (w/w) replacement of rice with amaranth (25A). In the second phase of the study, 50% replacement of rice was carried out with cereals in combinations (25% each, w/w) such as amaranth + finger millet (AF), amaranth + sorghum (AS), amaranth + pearl millet (AP), finger millet + sorghum (FS), finger millet + pearl millet (FP) and sorghum + pearl millet (SP), of which FS and FP batter variants were accepted by the panellists and taken ahead for further analysis. Control, 25F, FS and FP batter variants were subjected to various biochemical analysis up to 20 h of fermentation. Replacement of rice in these batter variants led to comparable changes with an increase in the levels of microbial counts, amylase, protease and phytase activities, titratable acidity, reducing sugars, soluble proteins and antioxidant activity during fermentation. A greater reduction in trypsin inhibitor activity (TIA) was also observed. Idlis prepared with replacement of rice by other cereals (25F, FS and FP) resulted in improved textural values and bulk density as compared to control idlis, though the colour was affected.

Determinants of the diurnal course of salivary alpha-amylase

OBJECTIVE

Previous data from our group and others have shown that salivary alpha-amylase activity increases in response to stress. It has been suggested that salivary alpha-amylase may be a marker for adrenergic activity. Less is known about other determinants of salivary alpha-amylase activation. The objective of the current study was to describe the diurnal pattern of salivary amylase and its determinants.

METHODS

Saliva samples were collected immediately after waking-up, 30 and 60 min later, and each full hour between 0900 and 2000 h by 76 healthy volunteers (44 women, 32 men). Compliance was controlled by electronic monitors. In order to control factors which might influence the diurnal profile of salivary alpha-amylase (such as momentary stress, mood, food, or body activity), at each sampling time point the subjects filled out a diary examining the activities they had carried out during the previous hour.

RESULTS

Salivary alpha-amylase activity shows a distinct diurnal profile pattern with a pronounced decrease within 60 min after awakening and a steady increase of activity during the course of the day. Mixed models showed a relative independence of diurnal salivary alpha-amylase from momentary stress and other factors, but significant associations with chronic stress and mood.

CONCLUSIONS

Our results suggest that diurnal profiles of salivary alpha-amylase are relatively robust against momentary influences and therefore may prove useful in the assessment of sympathetic nervous system activity. The findings underscore the need to control for time of day in studies using salivary alpha-amylase as a dependent variable.

Effect of various types of fermentation on in vitro protein and starch digestibility of differently processed pearl millet

Pearl millet (Pennisetum typhoideum) grains were fermented with Lactobacilli and yeast alone, in combination and with natural flora at 30 degrees C for 48 h after giving various processing treatments viz, fine and coarse grinding, soaking, debranning, dry heat treatment, germination and autoclaving after adding of water. Fermentation was carried out with Lactobacillus acidophilus and Rhodotorula isolated from naturally fermented pearl millet and Lactobacillus acidophilus, Candida utilis and natural fermentation using freshly ground pearl millet flour as inoculum. All the processing treatments except coarse grinding improved the protein and starch digestibility. Autoclaving enhanced the digestibilities of processed samples which was further improved by different types of fermentation, the maximum being in case of germinated and naturally fermented pearl millet. A combination of Lactobacilli and yeast was more effective in increasing the protein as well as starch digestibility as compared to pure culture fermentation.

Levels of antinutritional factors in pearl millet as affected by processing treatments and various types of fermentation

Pearl millet (Pennisetum typhoideum) was fermented with Lactobacilli or yeasts alone and in combination, and with natural microflora after various processing treatments, as grinding, soaking, debranning, dry heat treatment, autoclaving and germination. Fermentation was carried out at 30 degrees C for 48 hours with Lactobacillus plantarum (LP) and Rhodotorula (R) isolated from naturally fermented pearl millet and Lactobacillus acidophilus (LA), Candida utilis (CU) and natural microflora (NF). Germination and autoclaving, and debranning and autoclaving were the most effective processing treatments to reduce the phytic acid, amylase inhibitors and polyphenols. There was a further reduction in these antinutrients due to fermentation. Phytic acid and amylase inhibitors were completely eliminated after fermentation in some of the samples especially in soaked, debranned and germinated ones. Polyphenols were altered non-significantly in general but fermentation with Lp + R and NF caused a significant increase in polyphenols.

Effect of heat treatments on alpha-amylase inhibitor activity in sorghum (Sorghum bicolour L.)

The application of dry heat to sorghum seeds and meal was not effective in inactivating the amylase inhibitory activity. Overnight soaking followed by heat treatment was more effective in destroying amylase inhibitory activity. Cooking the meal, raw seeds and soaked seeds drastically reduced the levels of alpha-amylase inhibitory activity.