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Fermented millet products serve as a natural probiotic. Millets act as super foods
because as it is the reservoir of nutrients for better health and are rich in B vitamins,
calcium, iron, potassium, magnesium, zinc, dietary fibre and phytochemicals.
Probiotics are live microorganisms that when administered in adequate amounts confer
a health benefit on the host. Prebiotics are non-digestible ingredients that enhance the
activity of colon bacteria and the viability of probiotics. Synbiotics involve the
combination of probiotics and prebiotics. Hence, the present study entitled
“Standardisation and quality evaluation of millet based probiotic yoghurts” was
undertaken to develop probiotic and synbiotic yoghurts incorporating barnyard millet
and finger millet and to evaluate its acceptability, nutritional, health and shelf life
qualities.
Millet based yoghurts were prepared with different combinations of millet slurry
and milk using both barnyard and finger millet. Among these yoghurts prepared, 50 per
cent milk and 50 per cent millet slurry (from both barnyard and finger millet) were
found to be the best with the total score of 51.94 for barnyard millet based yoghurt and
51.39 for finger millet based yoghurt. The addition of L. acidophilus made this yoghurt
a probiotic after optimising the growth conditions for L. acidophilus, with regard to
substrate concentration, temperature, time and inoculum concentration. The maximum
growth was seen with 25 g of yoghurt sample fermented for 6 h with 1 ml of probiotic
culture (L. acidophilus) with 2 ml of yoghurt culture at 38º C. The viability of L.
acidophilus in barnyard millet based probiotic yoghurt was 9.02 log cfu / ml and in
finger millet based probiotic yoghurt was 8.98 log cfu / ml. The prepared probiotic
yoghurt of both millet based were stored for 15 days and its qualities were analysed and
compared with non-probiotic yoghurt of each millet, at 5 days interval.
The physico-chemical composition, health studies, organoleptic evaluation,
population of L. acidophilus and enumeration of total micro flora were analysed and
found that moisture, acidity, water holding capacity, viscosity, cohesiveness,
gumminess, resilience, protein, fat, total ash, minerals, in vitro mineral availability of
minerals (calcium, iron, potassium, phosphorus, zinc and magnesium) and antioxidant
activity were higher in probiotic yoghurt of both millets than in non-probiotic control.
The other parameters such as pH, syneresis, carbohydrate, TSS, reducing sugar, total
sugar and crude fibre were higher in non-probiotic yoghurt than probiotic yoghurt in
both millets. On storage each parameters decreased except moisture, acidity and
syneresis which was shown to increase.
The acidity of probiotic and non-probiotic yoghurt of barnyard millet based
yoghurt was found to be 0.81 and 0.72 per cent respectively and for finger millet based
it was 0.72 and 0.78 per cent for non-probiotic and probiotic yoghurt respectively. For
probiotic and non-probiotic yoghurt of barnyard millet was found to be 8.58 g/100 g
and 8.76 g/100 g for carbohydrate and 3.52 and 3.49 g/100 g for protein. In the case of
finger millet based non-probiotic and probiotic yoghurt, carbohydrate found to be 8.91
and 8.32 g/100 g. The protein content of finger millet based probiotic and non-probiotic
yoghurt 3.89, 3.91 g/100 g respectively. Fat was high in probiotic yoghurt of both
millets (0.63 g/100 g for barnyard millet and 0.39 g/100 g for finger millet based
yoghurt). In the case of non-probiotic yoghurt the fat content of barnyard millet based
yoghurt was 0.59 g/100 g and 0.28 g/100 g for finger millet based yoghurt. The crude
fibre of barnyard millet based probiotic and non-probiotic yoghurt and finger millet
based probiotic and non-probiotic was 0.50, 0.60, 0.90, 1 g/100 g respectively.
The water holding capacity was less in probiotic yoghurt (79.75 per cent for
barnyard and 78.30 for finger millet based yoghurt) than non-probiotic yoghurt (88.30
per cent for barnyard millet based yoghurt and 85.80 per cent for finger millet based
yoghurt). The syneresis of barnyard millet based probiotic and non-probiotic yoghurt
was 5.20 and 4.33 per cent respectively. For finger millet based yoghurt the syneresis
of non-probiotic yoghurt was 4.33 per cent and 5.10 per cent for probiotic yoghurt. The
viscosity was high in probiotic than non-probiotic yoghurt, for barnyard millet yoghurt
the viscosity was 21104 cP for non-probiotic and 23204 cP for probiotic yoghurt. In the
case of finger millet based yoghurt the viscosity was 20900 cP for non-probiotic and
22800 cP for probiotic yoghurt.
The calcium content of barnyard millet based non-probiotic and probiotic
yoghurt and finger millet based non-probiotic and probiotic yoghurt was 58.43 mg/100
g, 59.36 mg/100 g, 72.06 mg/100 g and 73.18 mg/100 g respectively. The iron content
of barnyard millet based non-probiotic and probiotic yoghurt and finger millet based
non-probiotic and probiotic yoghurt was 0.24 mg/100 g, 0.25 mg/100 g, 0.23 mg/100 g
and 0.24 mg/100 g respectively.
The bioavailability of minerals in probiotic yoghurt of both millet based
yoghurts was higher than non-probiotic yoghurt. On Storage bioavailable calcium was
decreased to 77.13 per cent for non-probiotic and 78.07 per cent for probiotic yoghurt
of barnyard millet based yoghurts and in the case of finger millet based yoghurt it was
77.13 per cent for non-probiotic yoghurt and 72.54 per cent for probiotic yoghurt. The
bioavailability of iron for barnyard millet based probiotic yoghurt was 70.02 per cent
and non-probiotic yoghurt was 69.82 per cent initially. For non-probiotic yoghurt and
probiotic yoghurt of finger millet based was 775.96 per cent and 76.98 per cent of in
vitro iron respectively.
On storage, the viability of L. acidophilus decreased and on the 15th day it was
11.11 and 11.07 log cfu/ml for barnyard and finger millet based yoghurts respectively.
On microbial enumeration, the bacterial count was 6.54 and 7.18 log cfu/ml for
barnyard millet based non-probiotic and probiotic yoghurts. The bacterial count for
finger millet based probiotic and non-probiotic yoghurts was found to be 6.48 and 7.16
log cfu/ml. There was no fungal and yeast growth initially and on the 15th day, fungi
growth was found to be 1 cfu/ml for both barnyard and finger millet based yoghurts, but
it was within the permissible limit.
Synbiotic yoghurts were standardised with the addition of inulin and
polydextrose with varying percentages. The addition of 3 per cent of these prebiotics to
the yoghurt with 50 per cent milk, 50 per cent millet slurry were found to be the best.
Compared to synbiotic yoghurt made with inulin and polydextrose, probiotic
yoghurt had a lower carbohydrate, higher protein and fat. In case of synbiotic yoghurt
carbohydrate content varied from the range of 8.14 - 8.47 g/100 g, protein between 3.61
- 3.99 g/100 g and fat ranged from 0.42 - 0.69 g/100 g. The textural properties such as
water holding capacity, syneresis and viscosity of synbiotic yoghurt was in the range of
79.32 - 80.73 per cent, 5.04 - 5.15 per cent and 23310 - 25203 cP respectively.
The calcium content of barnyard millet and finger millet based probiotic yoghurt
was 59.36 mg/100 g and 73.18 mg/100 g, respectively. In case of synbiotic yoghurt it
varies from 60.02 - 74.26 mg/100 g.
The bioavailability of calcium was found to be 78.91 and 78.84 per cent for
inulin added polydextrose added barnyard millet based synbiotic yoghurts and 73.15
and 73.64 per cent for polydextrose added of finger millet based yoghurt respectively.
The in vitro iron content was 71.10 and 72.31 per cent for inulin added barnyard and
finger millet based yoghurts and 78.01 and 78.61 per cent for polydextrose added
barnyard and finger millet based yoghurts respectively.
The viability of L. acidophilus of inulin added barnyard and finger millet based
yoghurts was 11.16 and 11.15 log cfu / ml and for polydextrose added barnyard and
finger millet based yoghurts was 11.17 and 11.18 log cfu / ml.
The cost of production of the selected barnyard millet based probiotic yoghurt
was Rs. 21.65 / 100 g and for finger millet based probiotic yoghurt it was Rs. 23.74 /
100 g. The cost for inulin and polydextrose added barnyard millet based synbiotic
yoghurt was Rs. 25.76 / 100 g and Rs. 26.66 / 100 g and for inulin and polydextrose
added finger millet based yoghurt was Rs. 26.88 / 100 g and Rs. 27.88 / 100 g.
Probiotic yoghurt is a popular functional food product around the world.
Delivering an appropriate number of viable probiotic bacteria is critical in determining
the health improving properties of yoghurt. Prebiotics and probiotics both support the
body in building and maintaining a healthy colony of bacteria and other
microorganisms, which supports the gut and aids digestion. So the fermentation of
millet with probiotics can enhance the availability of nutrients and aid better health.