Influence of glucosamine caramel addition on physicochemical characteristics, and sensory attributes of soy sauce / Chan Ai Chee

Faculty of Industrial Sciences and Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang - 2026

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Caramel is generally added to soy sauce to enhance its colour, flavour, and antioxidant properties, but it also increases the MRPs which are detrimental to health. Glucosamine caramel offers functional benefits including flavour enhancement, antioxidant activity and reduces formation of harmful compounds compared to conventional caramel. However, most previous glucosamine caramel studies used temperatures less than 70 ºC, leaving higher temperatures unexplored. This research addresses the gap to optimize antioxidant and volatile carbonyl compounds for food applications. Glucosamine caramel was prepared in water, sodium phosphate or sodium acetate solutions at elevated temperatures (80–120 ºC) for 1 and 2 hours. Its physicochemical properties, including pH, browning intensity measured by UV-spectrophotometer, and colour determined using a colourimeter, were evaluated. The antioxidant activity of glucosamine caramel was assessed using ABTS and DPPH assays and reported as Trolox equivalent. The volatile carbonyl compounds were measured using Headspace Solid-phase Microextraction coupled with Gas Chromatography-Mass Spectrometry (HS-SPME GC-MS). Acetate-based caramel prepared at 120 °C for 1 hour was exhibited favorable properties, such as a greenish-blue hue, higher pH, high antioxidant activity (ABTS: 185.79 ± 17.89, DPPH: 124.31 ± 5.74 mM TE/ L), and comparable levels of volatile carbonyl compounds. This caramel was added to soy sauce to make glucosamine caramel soy sauce. It was then compared with commercial soy sauce (control) and glucosamine soy sauce (control) for volatile carbonyls, antioxidant activity and sensory evaluation. For the sensory evaluation, the result demonstrated that glucosamine caramel soy sauce had comparable acceptance to commercial soy sauce (p>0.05) in terms of saltiness, sweetness and overall acceptance. For antioxidant properties, glucosamine caramel soy sauce showed strong antioxidant capacity (DPPH: 262.35 ± 8.66 mM TE/mL, which was comparable to that of commercial soy sauce: 285.20 ± 39.87 mM TE/mL, p>0.05). Analysis of volatile compounds showed a higher level of diacetyl (74.53 ± 4.27 ppb, p<0.05) in glucosamine caramel soy sauce, which is related to enhance buttery notes. This research introduced glucosamine caramel as a functional alternative ingredient for soy sauce products, potentially improving antioxidant properties, flavour and comparable sensory attributes in soy sauce.