Influence of extrusion on expansion, functional and digestibility properties of whole sweetpotato flour

Beerwah Gold, Northern Star, Snow White, and L49 cultivars of sweetpotato from Australia and Papua New Guinea, were studied for their extrusion behaviours in a co-rotating twin-screw extruder at three moisture (30, 35, 40 g/100 g) and screw speed (150, 220, 300 rpm) levels with a slit die. Low moisture increased the die pressure (2-6 bar) and specific mechanical energy (280-600 kJ/kg) of the extruder. Expansion, functional and digestibility properties of the extrudates were extrusion-dependent and cultivar-specific. Extrusion moisture increased the longitudinal expansion (15-30 m/kg) of the extrudates, which were almost completely gelatinised (100 g/100 g degree of gelatinisation). In-vitro starch digestion revealed that salivary-gastric digestion in the extrudates ranged from 8 to 18 g/100 g dry starch, while the rate of starch digestion was 3.0-3.7 min-1. Salivary-gastric digestion in the non-extrudates was from 2 to 11 g/100 g dry starch, with the rate of starch digestion being 0.1-0.8 min-1. Estimated glyceamic index of the extrudates ranged from 87 to 124 g/100 g, higher than in the non-extrudates and dependent on extrusion moisture and screw speed. This is the first study on extrusion-property relationships of the cultivars to guide global utilisation of sweetpotato

Carotenoid contents of extruded and non-extruded sweetpotato flours from Papua New Guinea and Australia

Carotenoid contents of extruded and non-extruded flours of Papua New Guinean and Australian sweet-potato cultivars were studied, using spectrophotometry and high performance liquid chromatography (HPLC). The cultivars differed (p < 0.05) in their total carotenoid and β-carotene contents, and the Original Beauregard cultivar had the highest total carotenoid and β-carotene contents among the cultivars. The spectrophotometry (84.1720 μg/g solids) method generally over-estimated the total carotenoid content compared to the more specific HPLC (23.355 μg/g solids) method. Extrusion significantly (p < 0.05) decreased the ΔL*. Hunter colour values, while the Δa*., Δb*., total colour change (ΔE), chroma (CR), and browning indices (BI) increased. With the extruder and screw configuration used, extrusion at 40% moisture and 300 rpm screw speed retained carotenoid maximally at more than 80%. This study reports, for the first time, carotenoids of flours from south Pacific sweetpotato cultivars, and carotenoid retention during extrusion. Crown Copyrigh

The use of sweet potato (Ipomoea batatas (L.) Lam) root as feed ingredient for broiler finisher rations in Papua New Guinea

Accepted 14 January 2016The use of non conventional feedstuffs in poultry rations is now a common practice in developing countries where most of the ingredients used in the production of commercial poultry stockfeed are imported grains. The prices of these grains are dictated by world market prices and this translates into high retail prices for the end users. The purpose of this review is to highlight the potential of sweet potato root as a poultry feed ingredient especially for finishing off broilers in Papua New Guinea where this root crop is in abundance. This review discusses in general the metabolisable energy value of this crop when compared to maize and its impact on the intake of broilers when processed differently and fed at various inclusion rates. Trypsin inhibitors are the major anti-nutritive factor present in sweet potato roots; however these are eliminated with heat moisture treatments. The dietary fibre in sweet potato roots have been shown to have anti-microbial and prebiotic attributes which may be beneficial in promoting good gut health in chickens. The use of exogenous enzymes in sweet potato diets is briefly mentioned in this review. All in all, sweet potato roots can be included in diets for broiler chickens at 30% without adversely affecting intake of birds if processed correctly. However, to date limited information is available on how sweet potato can enhance digestive capacity of broiler in terms of gut morphology and digestive enzyme activities, as well as the shedding of the main zoonotic bacteria such as Campylobacter and Clostridium perfringens. The shedding of these bacteria in relation to food safety is important if sweet potato is to be used regularly in finishing off broilers in PNG.J. Pandi, P. Glatz, R. Forder, W. Ayalew, J. Waramboi, K. Chousalka

Characterisation of sweetpotato from Papua New Guinea and Australia: Physicochemical, pasting and gelatinisation properties

The physicochemical and functional properties of flours from 25 Papua New Guinean and Australian sweetpotato cultivars were evaluated. The cultivars (white-, orange-, cream-, and purple-fleshed, and with dry matter, from 15 to 28 g/100 g), were obovate, oblong, elliptic, curved, irregular in shape, and essentially thin-cortexed (1-2 mm). Flour yield was less than 90 g/100 g solids, while starch, protein, amylose, water absorption and solubility indices, as well as total sugars, varied significantly (p < 0.05). Potassium, sodium, calcium, and phosphorus were the major minerals measured, and there were differences in the pasting properties, which showed four classes of shear-thinning and shear-thickening behaviours. Differential scanning calorimetry showed single-stage gelatinisation behaviour, with cultivar-dependent temperatures (61-84 °C) and enthalpies (12-27 J/g dry starch). Oval-, round- and angular-shaped granules were observed with a scanning electron microscope, while X-ray diffraction revealed an A-type diffraction pattern in the cultivars, with about 30% crystallinity. This study shows a wide range of sweetpotato properties, reported for the first time