(Zea mays. L) extrudates - PSFST

weaning foods. Humans do not readily digest native
starch. Distinct several thermal processes, extrusion
cooking gelatinizes starch fairly low (12-22%) moisture
level. Increased temperature of barrel, shear force and
pressure in extrusion raise the level of gelatinization of
starch, but lipids, sucrose, dietry fiber and salts can
impede gelatinization (Jin t al, 1994). While full
gelatinization may not occur through extrusion,
digestibility is frequently enhanced (Wang, S et al, 1993).
Extrusion may progress protein digestibility by
denaturing proteins, revealing enzyme-accessible sites.
Globally the snack food industry is fetching up
bigger and more imperative every day. In the last ten
years, revolution in way of living and eating habits have
escort to an ongoing enhance in demand for snack foods.
The way of snacking in various countries can be
influenced by numerous aspects like as the diversity in
lifestyle in every area, the economic conditions, and
public accessibility of existing observation on nutritional
subject. Snacks can supply a better dietary intake of
essential amino acids and other food nutrients for
developing countries. Extrusion cooking is preferable
over other food-processing methods due to of constant
process with high efficiency and important nutrient
preservation, due to the high temperature and short
cooking time required (Guy, 2001).
There is a need to make use of locally-grown crops to
produce of suitable local recipes in the under developed
countries has been tense by international agencies as the
most efficient channel for addressing depending world
food harms (Iwe et a!. 2001). Maize is the cereal of major
importance in the developing world and has the maximum
genetic production potential of all the cereal crops.
Designing extruded snack foods today can be a difficult
process to meet up varying consumer’s tastes and
demands. The consumer’s requirement for “good for your
health” and “distinctive flavor” extruded snacks leads to
the indefinable exploration for something exceptional that
also demand to extensive range of peoples. Consequently
the current study has been designed to investigate the
effect of different extruder variables temperature, screw
speed and moisture content on the chemical and mineral
profile of two different maize cultivars.
Materials and methods
The current research was performed to determine
the suitability of maize cultivars for extrusion cooking and
effect of different extrusion parameters on quality of
product. The study proposed in this manuscript was
conducted at the “Extrusion Center”, National Institute of
Food Science and Technology, University of Agriculture,
Faisalabad.
Pakistan Journal of Food Sciences (2012), Volume 22, Issue 2, Page(s): 108-116
PAK. J. FOOD SCI., 22(2), 2012:108-116
ISSN: 2226-5899
Procurement of raw material
Two commercial maize cultivars namely
hybrid R-2303 yellow dent corn and R-2207 White
flint corn were procured from Rafhan Maize
Faisalabad.
Cleaning
Maize grains were cleaned physically to eliminate
dust particles, broken seeds, seeds of other crops and
other contaminants like as weeds and metals.
Preparation of raw material
Two commercial maize cultivars namely hybrid R-
2303 yellow dent corn and R-2207 White flint corn were
milled to obtain maize grits according to a milling
diagram proposed by Robutti et al., (2002).
Extrusion process
The maize cultivars were extruded through a singlescrew,
short barrel (90 mm) snack food extruder (Extru-
Tech, Inc.Model # KN, Sabetha, Ks 66534). The extruder
was fixed with a 2 start screw and a 2-hole die with 4mm
orifice. The prepared raw material, maize grits were fed
into the extruder at the rate of 20 Kg /h using a mass flow
feeding device. The extruder was run at different barrel
temperatures ranges between 110 and 150 °C. Energy
consumption during extrusion differs among the grits
extruded in the research. Extrusion cooking was initiate
to be a high-temperature, short-time process in which
moistened, extensive, starchy and protinacious food
materials are plasticized and cooked in a tube by a
permutation of moisture, pressure, temperature and
mechanical shear .The plastic foam set quickly as it left
the die, forming a light, crispy, firm material alike to
various well recognized snack foods. As the extrudates
come out from the die, it was cut into 10–12 mm long
snack-like extrudates with a revolving knife. Promising
extrudates were instantly spread on the laboratory table at
room temperature for 4 h before drying in the oven at 60
°C for 10 h to attain a final moisture content of 4-5% and
stored in plastic bags at room temperature for more
analysis.
Chemical analysis of maize grits and extrudates
Chemical analysis of maize grits and extrudates
were carried out by following the methods illustrated in
(AACC, 2000).
Moisture Content
The moisture content in maize grits and grounded
extrudates was estimated by drying samples in a hot air
oven at a temperature of 100± 5 °C until to a constant
weight. Moisture contents was determined by following
the method no 44-15A of AACC (2000).
The extruder variables applied in this study are given in
Table1
109