Development and characterization of extruded/expanded products containing pork and nonmeat ingredients

Abstract

Blends of pork lean (20%), defatted soy flour (25%), high-amylose corn starch and added water were extrusion-cooked using a laboratory-scale single-screw extruder (15:1 length-to-diameter ratio, 4:1 screw compression ratio, 6.35 mm die nozzle diameter). Experiments conducted according to a central composite rotatable design for response surface methodology and additions statistical techniques determined the extrusion condition that would result in extradites with high expansion ratio and low shear force to be 22.78% feed moisture, 160C̊ process temperature and any screw speed between 153-187 rpm. Response surfaces and predictive models indicated feed moisture to be the most influential extrusion variable, and process temperature secondary, to expansion ratio, bulk density and shear force values of the extrudates. Pork-soy flour-starch blends with or without additional nutmeat ingredients-onion powder (1%), alone or in combination with carrot powder (1.5%) or carrot extract (1.5%), or defatted oat flour (5%)-were formulated and extruded at 170 rpm screw speed, 22.78% feed moisture and 160C̊ process temperature. Instrumentally-measured hardness (shear force) of extrudates without the additional nutmeat ingredients was comparable to that of commercially available wheat-based snack sticks or pretzels. Additional ingredients generally decreased expansion and increased bulk density and shear force values. When extrudates with or without onion powder were evaluated by trained sensory panelists, "grain complex'' was the most intense flavor note. Addition of 1% onion powder to raw material mixes made "onion'' flavor distinctly detectable in extrudates. Peroxide values were a better indicator of lipid oxidation than 2-thiobarbituric acid-reactive substances values for these expanded, dry extradites with high protein and starch contents. The onion powder, carrot powder or extract, and defatted oat and soy products used here limited lipid oxidation in extradites stored at 37C̊ for 60 days. The base product-extrudates from pork-soy flour-starch blends without additional nutmeat ingredients-had low moisture (4%) and fat (3%) and contained 34% protein. Oleic acid was the predominant fatty acid (36% of total fatty acids). Essential amino acids were present in greater amounts in that product than in analogous snacks containing only corn. Since only small amounts of additional nutmeat ingredients were used in other test products, all products were considered to be higher in protein and lower in fat compared to some fried or baked, extruded cereal-based snacks.