investigated the moisture sorption isotherm characteristics of commercial
Kilishi. The adsorption and desorption of the Kilishi were determined at 30 oC
and 40 oC temperatures. The sorption Models of Guggenhein Anderson-De Boer
(GAB), Brunauer Emmett and Teller (BET), Oswin, and Henderson were each used to
describe the sorption isotherm of the meat at 30 oC and 40 temperatures and the percentage root mean
square (%RMS) of the various models used were determined in comparism with the
data generated in each model. The result revealed that the adsorption and
desorption isotherm of kilishi products were sigmoidal in shape ranging from
the monolayer region of bound absorbed
and immobile water through the concave region that represents the least
strongly bound which is relatively mobile. There was an effect of temperature
on the equilibrium moisture contents at 30oC and 40oC, which decreased with
increase in temperature at constant water activity, hence increase in
temperature increases the water activity at constant moisture content for BET,
GAB and Oswin Models, Monolayer moisture content (Mo) decreased with increase
in temperature for both adsorption and desorption while the % RMS decreased in
adsorption but increased in desorption. Henderson % RMS increased for
adsorption and decreased for desorption. Of all the sorption models chosen GAB
model gave the best description of the equilibrium moisture data for
Meat is the flesh of animals consumed for food (Aberle et
al., 2012). In the tropics, the bulk of
the meat consumed is derived from sheep, cattle, goats, pigs, deer, antelope,
rabbit, squirrel, rat, elephant, camel and other mammalian animals domesticated
or wild; poultry, including chicken, turkey, ducks, guinea fowls, geese and
meat from other avian and reptilian animals; fish, crayfish, crabs, lobster and
other sea foods; snails and other molluscs; and insects (Ihekoronye and Ngoddy,
1985). The bulk of the dietary protein in the Nation is obtained through
crops. The level of animal protein
intake is only about 17 percent of the total consumed by the average Nigerian,
which is inadequate from the minimum recommended. This situation could be
improved by developing the food processing sector especially meat and meat
products (Igene et al., 1997).
Meat drying is the oldest method of meat preservation. It
consists of a gradual dehydration of pieces of meat cut to a specific uniform
shape that permits the equal and simultaneous drying of whole batches of meat.
Kilishi is an example of Nigerian traditional dried meat, which is obtained
from sliced lean muscles of beef, goat or lamb.
It is made on a large scale under the hot and dry weather conditions
prevailing from February to May. It is
produced by sun drying thin slices of meat infused with spices and slurry of
defatted groundnut paste. Kilishi is
mainly produced by Hausa’s and Fulani’s. The product appears to have developed
as a means of preserving meat using a simple means when it is in surplus supply
by the early Fulani’s and Hausa’s in the absence of facilities for refrigerated storage.
The quality of most foods preserved by drying depends to a
greater extent upon their physical, chemical and microbiological stability.
This stability is mainly a consequence of the relationship between the
equilibrium moisture content (EMC) of the food material and its corresponding
water activity (aw) at a given temperature. These water sorption Isotherms are
unique for individual food materials and can be used directly to solve food
processing design problems, predict energy requirements, and determine the
proper storage conditions (Myara et al., 1996). Moisture sorption is the
relationship between the equilibrium moisture content of a material (expressed
as mass of water per unit mass of dry matter) and water activity at a given
Moisture sorption can be used to investigate structural
features of a food product such as surface area, pore volume, size distribution
and crystallinity. An Isotherm obtained by exposing material to air of increasing humidity is
termed the adsorption Isotherm while that obtained by exposing the material to
air of decreasing humidity is known as the desorption Isotherms. Moisture sorption
Isotherm equations can be used to predict moisture sorption properties of
foods. Many empirical and semi-empirical equations describing the sorption
characteristics of foods have been proposed. These include the Mono BET Models,
GAB Models, Henderson and Halsely Models, Smith, Oswin Models and others.
Labuza (1975b) attributed this to the fact that the water is associated with
the food matrix by different mechanisms in different water activity regions.
Models available in the literature to describe moisture sorption Isotherm can
be divided into several categories. These include the Kinetic models based on a
monolayer (Mod BET Model). Kinetic models based on a multi-layer and condensed
film (GAB model) semi-empirical (Henderson and Halsely models) and empirical
models (Smith and Oswin models).
The traditionally processed Kilishi delicacy is highly
cherished by consumers because of its diverse use and unique taste. However, it
poses a serious health hazard because of the handling and processing and
storage methods by the local manufacturers as well as the hawking system. All of these expose the pre and post
processed product to microbial contaminations.
Therefore, there is need to improve the processing, storage, packaging
and overall quality of Nigerian traditional food products.
The average Nigerian diet lacks animal protein. Although the
animal resources are available; the inadequate supply of meat products is due
to poor processing. The resulting
product has questionable qualities of short life and a large proportion is lost
due to spoilage.