TITLE:
Microbiological and Nutritional Assessment of Starter-Developed Fermented Tigernut Milk
AUTHORS:
Sherifah Monilola Wakil, Oluwatobi Tolu Ayenuro, Kubrat Abiola Oyinlola
KEYWORDS:
Tigernut Milk; Pasteurization; Fermentation; Starter-Development; Mixed-Culture
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.5 No.6,
March
7,
2014
ABSTRACT:
Fermented tigernut
milk (FTM) was prepared from three different varieties (fresh yellow, big and
small dry brown) of tigernut (Cyperus
esculenta) obtained from Bodija market, Ibadan, Oyo state. Fifty two
microbial isolates were obtained from FTM at different fermentation times, 32
of which were on MRS agar, 12 on nutrient agar and 8 on malt extract agar.
Lactic acid bacteria were identified as Lactobacillus
plantarum (LP), Lactococcus lactis (LC), Lactobacillus brevis, Lactococcus cremoris, Lactobacillus bulgaricus and Lactococcus thermophilus (LT). The non-LAB
identified includes E. coli, Bacillus species and Proteus species while the yeasts include Saccharomyces cerevisiae and Candida kefyr. Lactic acid bacteria were found to predominate the total
microflora of the FTM with their count ranging between 2.0 × 104 cfu/ml to 2.0 × 108 cfu/ml. Microbiological examination revealed
that the FTM was safe for consumption as non-LAB counts were below the limit of
acceptance which is 2.0 × 105 cfu/ml for dairy milk by Codex
Alimentarius Commission. The quantity of lactic acid produced by the LAB
isolates ranged between 0.86 g/l - 2.86 g/l while that of hydrogen peroxide
ranged between 0.16 g/l - 0.51 g/l. Starter cultures were selected based on
predominance of isolate, physiological characteristics, quantity of lactic acid
and hydrogen peroxide production. The tiger nut varieties were fermented with
the following starter combinations LP, LP/LC, LP/LC/LT, LP/LT while the fifth
was spontaneously fermented. The nutritional, chemical and sensory properties
of the starter fermented tiger nut milk were evaluated. The highest protein
content (24.80%) was obtained in FTM with mixed cultures of LP/LC/LT while the
least (3.00%) was obtained in spontaneously fermented milk. There was a
significant difference in the FTM varieties. The highest fat content (9.40%)
was obtained in spontaneously fermented tiger nut milk while the least (3.40%) was
found in FTM with mixed cultures of LP/LC/LT. Fermentation decreased the pH and
increased the lactic acid of the starter developed FTM, while sensory
evaluation test showed that the FTM with mixed cultures of LP/LC/LT was highly
acceptable. In conclusion, an excellent and acceptable FTM can be produced
using treatments which comprise of pasteurization at 90°for 15 minutes,
fermentation at 45℃for 18 hours using
mixed cultures of Lactobacillus plantarum, Lactococcus lactis and Lactococcus thermophilus.