Using freshly-extracted chia seeds mucilage as a stabiliser/emulsifier for Gelato ice cream : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Auckland, New Zealand

Abstract

Plant-derived hydrocolloids contain polysaccharides that can help improve food quality by improving food structure and texture and emulsifying and thickening properties. Seed plants that produce mucilage constituents, including flax, psyllium, yellow mustard, basil, and chia seeds, are among the most promising sources of hydrocolloids. Due to its unique physiochemical and conformational aspects from the hydrophobic and hydrophilic side groups, plant seed mucilage has a great water and oil-holding capacity. This study introduces a novel approach to gelato formulation, utilising the unique properties of freshly extracted chia seed mucilage. Notably, the mucilage contains uronic acid that can retain water up to 27 times its weight, demonstrating its potential for stabilising the mix and emulsifying activity. The mucilage was extracted at 80°C for 2.5 hours with a 1:20 seed-to water ratio and was evaluated for its ability as a stabiliser/emulsifier in gelato. With an average extracted mucilage of 4.61 ± 0.39 g (w/w) and an average pH of 6.8 ± 0.07, the mucilage was used in various concentrations: 1.75%, 2%, 2.25%, and 2.5%. The gelato formulations made with chia mucilage in place of commercial stabiliser were characterised. The pH, fat globule size distribution, overrun, meltdown rate, rheological properties, and texture were determined. The microbiological activity of Listeria and viable microbes from the product were checked. The gelato samples were evaluated and discussed through focus groups. The chosen gelato formulation was put through a consumer sensory evaluation to affirm its acceptance. The best formulation contained 2.25% (w/w) mucilage, which was incorporated into a premade gelato mix at 4000 rpm and mixed for 10 min. Its pH was 6.51 ± 0.03, with an overrun of 24.77 ± 0.94 (v/v), a total meltdown rate of 0.38 ± 0.004 g/min, the fat globule size in the gelato mix was 0.28 ± 0.081 mm while in the gelato melt it was 0.49 ± 0.08 mm. The frozen gelato with 2.25% chia seed mucilage had a hardness of 65.59 ± 8.91 N. No Listeria was detected, and <10 viable microbe colonies were detected in the gelato, indicating a hygienic and clean manufacturing, handling, and storage process. The focus group agreed that the best formulation had a creamy consistency without ice crystals. This result was supported by the consumer sensory evaluation that deemed the attributes to be Just-About Right without any off flavour and off textures from the mucilage. Overall, using chia mucilage as an emulsifier/stabiliser for gelato has shown potential and possibility for further evaluation and uses.