Characterization of basil (Ocimum basilicum L.) seed flour and its functionality in ice cream : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Palmerston North, New Zealand
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Date
2020
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Massey University
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Abstract
This study explored the functional properties of basil seed flour (BSF) by determining the effect of concentration (0.1-1.5% wt/wt), pH (3-9) and ionic strength (0-1M) on the solution and emulsifying properties of BSF solutions and oil-in-water emulsions. The emulsifying properties of BSF were evaluated in terms of particle size and its distribution (d₃₂ and d₄₃), the rheological properties and the droplet charge. The visual phase separation of these emulsions after storage for one month at 20 °C and thermostability studies both at lower pasteurisation temperature (80 °C for 30 minutes) and higher retorting temperatures (121.1 °C for 15 minutes) were carried out. Finally, application trials in ice cream were done at two different test concentrations of 0.6% and 2.3% wt/wt. The use of flour resulted in higher particle size data which was due to the lesser surface active material present in the flour components. However, at 1.5% BSF concentration, there was no visual phase separation after one month’s storage period due to the plethora of components in the milled fractions of BSF, especially the lignin component acting as a Pickering emulsifier at these elevated levels of BSF. There was increase in the particle size when the pH was reduced due to the aggregation of the polysaccharide fractions. This was reversed as the alkalinity in the system increased showing smaller particle sizes. The protein component contributed to the electrostatic stabilisation of the droplets above the isoelectric point and the polysaccharide fractions contributed to the steric stabilisation, thus resulting in stable emulsions. The salt addition led to instabilities in the systems. The viscoelasticity and yield stress combinedly provided by other components in the BSF were lower than basil seed gum (BSG) and led to phase separation with salt addition especially at 1M concentration. The pasteurisation of the emulsions resulted in flocculation of the emulsions whereas retorting led to thermal hydrolysis of the proteins at elevated temperatures. However, at 1.5% BSF concentration there was possible network formation and thus showing improved stability for the stored emulsions. Finally, in the ice cream application, higher aeration and smoothness were seen with 2.3% BSF concentration than at 0.6% BSF concentration. There was 27% reduction in the meltdown rate for the highest test sample ice cream compared to the lowest test sample. Overall, BSF showed promising characteristics of a natural emulsifier.
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Figure 8 (=Silva et al., 2015 Fig 2) was removed for copyright reasons.