Locust bean gum hydrolysis : impact on molecular and functional properties : a thesis presented in partial fulfilment of the requirements for the degree of Master in Food Technology, at Massey University, Manawatu, New Zealand
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Date
2021
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Massey University
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Abstract
Locust bean gum (LBG) is a widely encountered additive in the food industry, with particular
application in ice cream production, functioning as a viscosifier and stabilizer, where it
reduces ice crystallization and slows down the melting rate. However, its incompatibility
property with milk proteins, especially when mixed under high concentrations can lead to
phase separation and wheying, often necessitating the use of additional stabilisers such as
carrageenan, to mitigate this issue. Enzymatic hydrolysis was hypothesised as a potential
method to modify the LBG structure, and thus its phase behaviour, by breaking native LBG
chain into fractions with lower molecular weight. It was also anticipated that this would also
reduce the LBG viscosity in solution.
In this study, the rheological behaviour of LBG during enzymatic hydrolysis was explored and
the impact of hydrolysis on phase behaviour in model LBG/skim milk powder (SMP)
solutions containing milk protein was studied. The effect of hydrolysis of LBG on its
functional properties in ice cream was also investigated.
β-mannanase was chosen to hydrolyse the LBG. Rheological results indicated that the
enzymatic hydrolysis could be used to progressively reduce relative viscosity of solution,
noting that termination of the reaction was made challenging by the high heat stability
observed for the enzyme. The results of Confocal Laser Scanning Microscope (CLSM) as well
as the phase diagram plotted for LBG/SMP mixtures implied that hydrolysis of LBG slowed
down the phase separation process. This was also evident when being applied in the ice
cream making. Hydrolysis of LBG showed a more compatible result with protein during the
aging stage. Interestingly, hydrolysis of LBG did not have significant effect on other
properties in the ice cream, with a relatively low overrun value (73.3%) compared to the
non-hydrolysed LBG (94.4%), and a slightly higher meltdown rate (0.26g/min) compared to
the normal LBG (0.24g/min).
Overall, hydrolysis of LBG can improve the compatibility of polysaccharide/protein mixtures
and has a promising prospect to be applied in the food industry.
Description
Figure 2.3 (=Dhawan & Kaur, 2007 Fig 2) was removed for copyright reasons.