Third generation extruded snacks with ancient grains : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand

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Massey University
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Third generation (3G) is a term that refers to the levels of processing used to produce a finished product. A 3G snack product starts with a starch based recipe that is extrusion cooked, formed into a dense shaped pellet and then dried. At this point, it is referred to as semi or half product because it needs to be further puffed to develop its texture and flavour. The objective of this project was to develop an unflavoured cereal-based 3G snack formulation with ancient grains. The snack must be unique in shape and suitable for hot air-puffing. Two 3G wholegrain base formulations were developed. One formulation was made from coarse rice flour, wholemeal wheat flour, potato starch, ancient grain blend (one third amaranth, one third quinoa and one third millet), wheat fibre 600 and salt. The second formulation was maize based by replacing coarse rice flour with maize polenta. These two base formulations contained ancient grains and nutrients that provide health benefits and were suitable for air-puffing. A lab-scale model Clextral BC21 twin screw co-rotating extruder was used for this study. Pasting properties of samples were evaluated using the Rapid Visco Analyser. It was found that ingredient selection and extrusion processing affected extruded pellets’ paste viscosities, the die swell and product expansion. Pasting properties of raw ingredient blend were affected by amylose and lipid content, and particle size of the cereal flour. The more even the raw material particle size was, the more even was the hydration of the material in the extruder. The results showed that inclusion of dietary fibre (wheat fibre 600, Beneo GR or Hi-MaizeTM 1043) in the 3G formulations decreased raw ingredients’ and extruded pellets’ paste viscosities, which resulted in reduced pellet expansion. It was found that wheat fibre 600 at 4 % was the best fibre choice to produce a 3G snack, because it accelerated extruded pellet drying, helped in ‘pellet checking’ control and producing more uniform cell sized expanded products. Hi-MaizeTM ingredients were found to lead to the deterioration of viscosity and snack pellet expansion, and therefore not recommended to be used for 3G snack base formulation. Increasing the water injection rate to the extruder (from 1.0 to 1.7 L/h) decreased the extruder apparent torque, thrust pressure, die pressure and SME. The degree of starch degradation was also reduced, but the product expansion was increased. Pellet expansion was found closely correlated to the pasting properties of the raw ingredient blend. Pellet expansion increased with the increase of peak viscosity (PV) and final viscosity (FV) of the raw ingredient blend. A suitable laboratory drying method was developed for 3G snacks. It was found that drying and holding at 1 h ± 5 min intervals including a pre-drying step had minimal pellets defects. Humidity control (60 %) was required throughout this drying process. After puffing, the product sectional expansion index (SEI) increased with the increase in salt concentration from 0.5 % to 1.0 % and increase in moisture content from 9.5 % to 12.1 %. The extruded pellets moisture was found to have the most significant effect on the finished product expansion, and maximum expansion due to puffing was found at 10.6 % pellet moisture. A shear-compression analysis of the 3G product prototypes and competitor products showed that most of low moisture commercial snack products available in the market have low bulk density and were brittle. The products produced from the proposed 3G formulations were much harder than the commercial products. Qualitative consumer focus group studies were conducted to gain insights into consumers’ attitudes towards extruded snacks, desirable texture and product claims to be included in the product. The results showed that five themes typically associated with snack consumption (nostalgia, special social occasions, distraction, convenient treat and hunger). Taste and price were the most important to the participants, and the health benefits were only an extra bonus. Participants were not tempted by an ancient grain claim. Product prototypes did not receive very positive feedback due to the taste and the product size. Product texture was found acceptable by most participants. This study produced initial formulations for a 3G snack, provided a good starting point for understanding of the 3G extruded snack process and provided valuable information for further development work. Further work is required to scale up the recipe, to increase the snack size, to further improve of the 3G snack flavour without significantly increasing the salt content and to carry out a consumer acceptance study on the scaled up 3G snack products.
Grain, Ancient grains, Snack foods