Pomaces are low-value byproducts obtained when fruit and vegetable
products are processed. Tomato, grape and pomegranate pomaces as well as
barley are valuable sources of fiber and other compounds that are known
to be beneficial to human health.
Scientists wanted to produce an extruded barley-based snack into
which they would incorporate different types of pomace. Their findings
demonstrate the feasibility of developing value-added products from
fruit and vegetable pomace and barley flour blends.
In tests, the researchers determined the effects of extrusion
conditions on the physical properties of the extrudate. The barley flour
and pomace blends were extruded at 22% moisture content in a 30-mm
commercial co-rotating twin-screw extruder with five heating zones and a
slit die.
The scientists performed three-factor factorial designs for each
type of pomace-barley flour blend. Analysis of variance, a collection of
statistical models, was used to evaluate the effect of die temperature,
which ranged from 140 C to 160 C; screw speed, which ranged from 150 rpm
to 200 rpm; and pomace ratio-2% to 10%-on the flour's physical
properties.
Researchers analyzed the sectional expansion index (SEI), bulk
density, peak force and color. The values for SEI ranged from 0.83 to
2.09. Increasing the die temperature and pomace ratio caused a decrease
in the SEI. The response of the screw speed differed as a function of
the type of pomace. Peak force values decreased as die temperature,
pomace level and screw speed increased.
The bulk density ranged from 0.25 g per [cm.sup.3] to 1.24 g per
[cm.sup.3], but differed for the different types of pomace tested.
Hunter color values a and b increased, while L values decreased with an
increasing pomace ratio. Some acceptable products were produced. They
had bulk densities in a range of 0.35 g per [cm.sup.3] to 0.65 g per
[cm.sup.3], and a peak force of less than 10 N.
Further information. Kathryn McCarthy, Department of Food Science
and Technology, University of California-Davis, One Shields Ave., Davis
CA 95616; phone: 530-752-1487; fax: 530-752-4759; email:
klmccarthy@ucdavis.edu.
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