EFFECT OF SPRAY DRYING PARAMETERS ON PHYSICOCHEMICAL, FUNCTIONAL AND RECONSTITUTIONAL PROPERTIES OF GOAT MILK POWDER
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Date
2021
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ICAR-NDRI, KARNAL
Abstract
Increased awareness of lactose intolerance and allergic symptoms caused by the ingestion of cow
milk has led to search for alternatives. Goat milk is considered as a useful substitute owing to its
higher concentration of mono- and poly- unsaturated fatty acids, and medium chain triglycerides,
which are beneficial for human health, especially for cardiovascular conditions. The scattered
goat milk production in limited quantities, lack of adequate cold chain and transportation
facilities limits its availability nationwide throughout the year. Freeze dried goat milk powder
had been commercialized across the globe and the major brands in India are Aadvik Foods®,
Amul® and DNS Global Foods™. Owing to poor heat stability of goat milk and loss of nutrients
during spray drying, the production of spray-dried goat milk powder is still at infancy stage.
However, shelf-stable powder formulation using energy efficient and cost-effective spray drying
process offers attractive solution. Thus, the current study aims to optimize spray drying process
variables for the manufacture of goat milk powder. Response surface methodology coupled with
a Box-Behnken experimental design was used to investigate the influence of the feed rate (15-
25mL/min), feed TS (20-30%) and inlet drying temperature (170-190°C) on the physicochemical,
re-constitutional and functional properties of goat milk powder. The response surface
methodology analysis indicated negative effect (P˂0.01) of inlet drying temperature on loose
bulk density because higher inlet temperature rapidly removed the moisture leading to formation
of vapor impermeable layer on the surface of powder particles, thus preventing air removal from
the powder particles. Loose bulk density ranged from 0.272 to 0.484 (g/mL). Increased feed
concentration enhanced theloose bulk density of powder significantly (P˂0.01) due to lower
amount of occluded air content.Water activity increased from 0.134 to 0.207 with increasing feed
rate from 15 to 25 mL/min. The interaction between feed rate and inlet drying temperature
influenced the colour L* value negatively (P˂0.01). With increasing inlet drying temperature
from170 to 190oC, L* value decreased from 87.171 to 86.582. Solubility has varied from 96.70
to 98.8 (%), it decreased with increasing total solids because of higher residence time required to
achieve desired concentration thereby resulting in denaturation of β-lactoglobulin followed by its
aggregation with casein and leading to higher amount of insoluble matter. Increase in feed TS
increased the dispersibility of powder significantly (P˂0.01), whereas an increase in inlet air
temperature reduced the dispersibility (P˂0.01). Wetting time ranged from52.666 to 91.666
(sec). Feed rate had a significant (P˂0.01) negative effect on both flowability and hygroscopicity,
whereas increasing feed TS increased the hygroscopicity of milk powder. There was no
significant (P˃0.05) effect of independent variables on water and oil binding capacities of goat
milk powder. Inlet drying temperature had a significant (P˂0.01) negative effect on emulsifying
activity, whereas increasing feed rate increased the emulsifying activity (P˂0.01). HMF content
was found to increase significantly with increasing inlet temperature. The optimized levels for
spray drying of goat milk powder were feed rate: 18.682mL/min, feed TS: 24.309% and inlet
drying temperature: 170oC, with a desirability of 0.751. FT-IR spectrograms of goat milk powder
produced at various temperatures yielded similar results, with no loss in any of the functional
groups.