Effects of Monk Fruit Sweetener on the Physicochemical, Microbiological and Sensory Properties of Strawberry Frozen Yogurt

Niau, Hui Ni (2024) Effects of Monk Fruit Sweetener on the Physicochemical, Microbiological and Sensory Properties of Strawberry Frozen Yogurt. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

This study investigated the effects of monk fruit sweetener (MFS) as natural sugar substitute on the physicochemical (texture, colour, viscosity, melting, titratable acidity, pH, total sugar content), microbiological (total bacteria, lactic acid bacteria, Streptococcus thermophilus count), and sensory (appearance, flavour, texture, and overall acceptability) properties of strawberry frozen yogurt. The effects of incorporating different amounts of MFS were also evaluated. Three formulations were tested: Control (6% sugar), F1 (Formulation 1: 6% MFS, total replacement of sugar), and F2 (Formulation 2: 2% MFS, reduced MFS). Texture analysis showed that hardness and gumminess significantly increased in F1 (3695.94 ± 654.04 gf and 2543.67 ± 315.06 gf), but the change was not significant in F2 (2283.91 ± 591.74 gf and 1659.18 ± 260.53 gf). Colour was affected also, with reduced lightness, increased redness and yellowness in F1 (L*: 64.75 ± 0.55, a*: 6.38 ± 0.10, b*: 22.95 ± 0.24) compared to Control (L*: 75.58 ± 0.43, a*: 3.90 ± 0.18, b*: 9.55 ± 0.10), though such effects were less prominent in F2 (L*: 72.68 ± 0.67, a*: 3.98 ± 0.32, and b*: 14.25 ± 0.97). Additionally, Control’s viscosity (168.00 ± 4.10 mPa·s), first dripping (6.61 ± 0.49 min), melting rate (0.49 ± 0.07 g/min), and complete melting (62.18 ± 2.28 min) significantly improved in F1 (194.55 ± 1.44 mPa·s, 8.79 ± 0.57 min, 0.28 ± 0.08 g/min, 71.73 ± 2.02 min, respectively), with non-significant changes in F2 (164.50 ± 1.50 mPa·s, 6.39 ± 0.47 min, 0.39 ± 0.03 g/min, 62.86 ± 1.56 min, respectively). Control’s pH (4.34 ± 0.02) significantly increased by MFS in F1 (4.41 ± 0.00) and F2 (4.41 ± 0.01), while total sugar was significantly lower in F1 (57.43 ± 0.28 mg/g) and F2 (54.06 ± 0.20 mg/g) compared to Control (140.43 ± 0.17 mg/g). There were significant reduction in lactic acid bacteria and S. thermophilus counts of F1 (5.85 ± 0.19 x 104 cfu/mL and 3.53 ± 0.28 x 106 cfu/mL) and F2 (4.90 ± 0.27 x 104 cfu/mL and 2.88 ± 0.26 x 106 cfu/mL) as compared to that of Control (6.83 ± 0.43 x 104 cfu/mL and 4.53 ± 0.46 x 106 cfu/mL). For all sensory attributes except sweetness and smoothness, there were significant differences in ratings between Control and F1, as well as between F1 and F2, but F2 received similar (p > 0.05) ratings to the Control. Similar scores of overall liking between Control (6.50 ± 1.36) and F2 (6.13 ± 1.43) suggest that a reduced amount of MFS is a feasible sugar substitute with sensory acceptability comparable to that of regular sugar.