CHAPTER ONE
1.1 INTRODUCTION
Yogurt is produced by a fermentation
process during which a weak protein gel develops due to a decrease in the pH of
milk (Oroian et al, 2011). The gel
structure contributes substantially to the overall texture and organoleptic
properties of yogurt and gives rise to shear and time development viscosity
(Odoneell and Butter, 2002).
Texture is one of the most important
attributes used by consumers to assess the quality of yogurt. The most frequent
defects related to yogurt texture that may lead to consumer rejection are
apparent viscosity variations and the occurrence of Syneresis (Kroger, 1975).
As a flow property, the Knowledge of the rheological properties is important
for design and evaluation of the process, process control, consumer
acceptability of the product and the optimization of process variables (Brennan
et al,1980; Dail and Steffe, 1990, a. b, Harrison and Gunningham, 1985). It is
important to establish relationship between structure and flow and to correlate
physical parameters (Abu-jdayil, 2003; Resch 2002).
Yogurt rheological characterization
is required for product and process development and to ensure consumer
acceptability (Benezech and Mangonnat, 1994). It is also required for effective
design of process system.
Yogurt from animal milk has received
a lot of scientific attention by many authors, but studies providing
information on the rheological characterization of legume yogurt like product
is scanty.
It is noteworthy, that the dairy sub
sector in Africa is thus relegated to the category of subsistence system of
production due to minor and peripheral status accorded the sector by various
government policies allied with the above, are poor nutrition and genetic
constitution of the Africa breeds of ruminant. The above problem leads to insufficient
milk availability of 15L of milk. This dramatic decrease in the consumption of
milk products stimulated in part the processing of milk from different seeds
and nuts.
Though undervalued in the past, milk
from plant source are key ingredients in the diet of African countries.
Recently, researchers have shown strong interest in these milk sources due to
their high nutritional values and economic potentials. It is worthy repeating
that milk sources form plants are seen as a radiating hope as well an ally in
the fight against hidden hunger. All the nuts and the seeds of interest in the
present study are found on the tropical environment including Nigeria for
various purposes.
1.2 OBJECTIVE
1. The
objective of this study will be to evaluate the rheological characteristics of
yogurt blends with tiger nut milk and coconut milk.
2. To
evaluate the physical properties of yogurt blends with tiger nut milk and
coconut milk.
3. To
determine the sensory quality of the yogurt blends with tiger nut milk and
coconut milk.