Effect of concentration on Liluva as food ingredient : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

With the application of spray drying, the content of soluble fibre in split yellow pea’s soaking and cooking water was decreased from 37% to 25.2% and 30% to 17.4%, which is mainly due to the loss of sugar during spray drying. While the protein contents in spray-dried and freeze-dried pea’s powder samples showed no significant difference with that in pea’s raw water, with around 30%. This could because freeze drying is a non-thermal treatment that will not denature the protein. While even though heat is used in the spray drying method to dry material, the treatment time might be too short to denature proteins. Furthermore, the general content of lysine in pea’s spray-dried powder was the lowest, followed by pea’s raw water and pea’s freeze-dried powder. It is possibly because of the occurrence of Maillard reaction in spray drying decreased lysine’s content. The analysis of the protein profiles in pea’s raw water and powder diluted water samples indicated that pea’s proteins did not be greatly changed by drying methods because they showed similar protein bands. Among proteins, the molecular weight of 99kDa, 25kDa, 15kDa, and 11kDa represented for lipoxygenase, 11S globulin unit, 7S globulin unit, and albumin, respectively. In terms of the distributions of particle sizes in pea’s raw water and powder diluted water samples, spray drying decreased pea’s particles sizes while freeze drying increased pea’s particles sizes. The decrease of particles sizes in peas is because of the heat treatment and atomization effect in spray drying. While the occurrence of particle aggregation during the forming of ice crystals in freeze drying increases of pea’s particle sizes. Particles sizes in pea’s samples also found to correspond to the colour of peas powder. Small particles sizes in spray-dried pea’s powder lighten the colour more significantly than freeze-dried powder because more lights will be refracted by smaller size particles, which has a larger surface area. However, freeze-dried powder showed redder and yellower colour than spray-dried powder. This could because the degradation or isomerization of the pigments (such as carotenoid or phenolics) in heat treatment in spray drying decrease the red and yellow colour. When comparing the foaming ability of pea’s raw water and pea’s powder diluted water samples under the same concentration (5%), we can see that drying had no significant influences on the foaming ability of pea’s water, with around 95%. While the effect of drying on pea’s emulsifying activity needed further experiment because of the improper usage of solvents in the dilution of emulsion. Last but not least, there were no significant differences in the sensory attributes (including appearance, aroma, taste, texture, and overall preference) of two sponge cake samples containing either pea’s raw cooking water or pea’s spray-dried cooking powder diluted water.