Standardization and sensory evaluation of Watermelon (Citrullus lanatus L.) RTS blended with Mint (Mentha piperita L.) and Lime (Citrus aurantiifolia S.)

Introduction

Modern science increasingly prioritizes the development of health-optimized functional foods and beverages to satisfy rising health consciousness and rapidly changing urban dietary habits (Slavin and Lloyd, 2012; Santos et al., 2020). Combining multiple plant matrices to build composite beverages has emerged as a key formulation strategy to maximize functional free and bound phenolics while balancing macro-nutrient profiles (Sayago-Ayerdi et al., 2021). However, primary raw materials like fruits are highly perishable commodities vulnerable to severe post-harvest losses during handling and logistics, especially across developing regions (Kader, 2005). Converting seasonal agricultural surpluses into value-added, non-fermented Ready-To-Serve (RTS) beverages serves as a practical methodology to alleviate these physical losses, improve annual availability and correct undesirable raw juice defects such as astringency or flavor separation (Sharma et al., 2022) [5,14,15,16,17] . Watermelon (Citrullus lanatus L.) is a widely cultivated, economically vital tropical fruit that contains 90-92% water, positioning it as an effective natural hydrator (Tarazona-Díaz et al., 2013). The fruit serves as an abundant source of lycopene, vitamins, and L-citrulline, a key amino acid that supports vascular health and reduces post-exertion muscle soreness (Perkins-Veazie et al., 2006; Burton-Freeman et al., 2022). Despite its nutritional advantages, pure watermelon juice features a high water activity and a relatively neutral pH, rendering it highly susceptible to rapid microbial proliferation and immediate sensory deterioration during storage (Chaudhary and Mendiratta, 2019; Liu et al., 2020) [1,2,8,11,19] . To counteract these stability limitations and elevate the consumer profile, blending the base juice with botanical extracts offers a viable solution (Sahu et al., 2017) [13] . Mint (Mentha piperita L.) delivers characteristic aromatic qualities alongside menthol-driven antimicrobial and antioxidant defense mechanisms (McKay and Blumberg, 2006) [10] . Concurrently, incorporating lime (Citrus aurantiifolia S.) introduces vital ascorbic and citric acids that lower matrix pH, improve flavour dimensions, and enhance biochemical stability against [4,9] . While separate baselines for fruit-herbal mixtures exist, extensive data regarding the exact standardization, physical adjustments of Total Soluble Solids (TSS) and longterm storage mechanics of an integrated watermelon-mintlime RTS system remains scarce (Kumar et al., 2021) [6] . This study aims to standardize a precise watermelon-mint-lime RTS formulation, providing a scientifically validated method for commercial shelf-life extension and agricultural waste reduction.

Materials and methods

The study was carried out in the Post-Harvest Laboratory, Department of Post Harvest management, College of Horticulture and Research station Durg (C.G), during the year 2024-25.

Raw materials

Fresh watermelon and lime fruits were procured from the local market of Durg, Chhattisgarh, while fresh mint leaves were collected from a kitchen garden at Amleshwar, Durg. Sugar, citric acid and sodium benzoate were used in beverage preparation, and sterilized glass bottles were used for packaging and storage.

Standardization of RTS

The various combinations of watermelon, mint and lime juice were used to determine the best combination for palatable RTS beverage through organolaptic evaluation  T0 Control Watermelon (100%)  T1 Watermelon (98%) + Mint (1%) + Lime (1%)  T2 Watermelon (97%) + Mint (1%) + Lime (2%)  T3 Watermelon (96%) + Mint (1%) + Lime (3%)  T4 Watermelon (97%) + Mint (2%) + Lime (1%)  T5 Watermelon (96%) + Mint (2%) + Lime (2%)  T6 Watermelon (95%) + Mint (2%) + Lime (3%)  T7 Watermelon (96%) + Mint (3%) + Lime (1%)  T8 Watermelon (95%) + Mint (3%) + Lime (2%)  T9 Watermelon (94%) + Mint (3%) + Lime (3%)

Preparation of RTS beverage

Fresh watermelon juice, mint extract and lime juice were prepared and blended with sugar syrup as per treatment combinations. The TSS and acidity were adjusted to RTS standards, sodium benzoate was added as a preservative, and the beverage was bottled in sterilized glass bottles and stored under ambient conditions for evaluation.

Storage studies

The prepared RTS beverages were stored at ambient temperature and analyzed at 0, 15, 30 and 45 days of storage for physicochemical and sensory parameters.

Sensory evaluation

The sensory acceptability of watermelon RTS blended with mint and lime was evaluated by a semi-trained panel of five judges from the College of Horticulture and Research Station, Sankra-Patan, Durg (C.G.). Evaluation was carried out using the 9-point hedonic scale described by Ranganna (1997) [12] . The coded beverage samples were presented randomly and assessed for taste, colour, appearance, flavour and overall acceptability under uniform conditions. Drinking water was provided between samples to avoid carry-over effects. The sensory scores obtained were statistically analyzed to identify significant differences among treatments and determine the most acceptable formulation.

Results and discussion Taste

The taste scores of watermelon-mint-lime blended RTS beverages decreased gradually during the 45-day storage period in all treatments. Initial taste scores ranged from 6.50 to 7.40, with T4 (Watermelon 97% + Mint 2% + Lime 1%) recording the highest score, followed by T5 and T1, while T0 (Watermelon 100%) showed the lowest score. Despite the decline during storage, T4 maintained the highest taste score (6.80) at 45 days and recorded the highest mean taste score (7.10), followed by T5 (7.00) and T1 (6.80). Lower scores were observed in T0 and T9. The reduction in taste may be due to biochemical and oxidative changes, degradation of sugars and organic acids, and loss of volatile flavour compounds. The results indicated that moderate incorporation of mint and lime improved flavour stability and taste acceptability during storage.

Colour

The colour scores of watermelon-mint-lime blended RTS beverages declined gradually during the 45-day storage period under ambient conditions. Initial colour scores ranged from 7.20 to 8.90, with T4 (Watermelon 97% + Mint 2% + Lime 1%) recording the highest score, followed by T5 and T1, while T9 (Watermelon 94% + Mint 3% + Lime 3%) showed the lowest score. Although colour acceptability decreased in all treatments, T4 maintained the highest score (7.00) at 45 days and recorded the highest mean colour score (7.95), followed by T5 (7.50) and T1 (7.33). The lowest mean scores (6.00) were observed in T0 and T9, with T0 recording the lowest colour score (4.50) at the end of storage. The decline in colour may be due to oxidation of natural pigments, nonenzymatic browning, and degradation of colour compounds during storage. The results indicated that moderate incorporation of mint and lime improved colour stability and maintained the visual quality of the RTS beverage throughout storage.

Appearance

The appearance scores of watermelon-mint-lime blended RTS beverages showed a gradual decline during the 45-day storage period. Initial scores ranged from 7.09 to 7.53, with T4 (Watermelon 97% + Mint 2% + Lime 1%) recording the highest score, followed by T1 and T5. At the end of storage, T4 retained the highest appearance score (7.34), while T9 (Watermelon 94% + Mint 3% + Lime 3%) recorded the lowest (6.61). The highest mean appearance score was observed in T4 (7.43), followed by T1 (7.35) and T5 (7.31), whereas T9 showed the lowest mean score (6.84). The decline in appearance was attributed to sedimentation, turbidity changes and pigment degradation. The results indicated that moderate levels of mint and lime improved appearance retention and visual stability during storage.

Flavour:

The flavour scores of watermelon-mint-lime blended RTS beverages decreased gradually during the 45day storage period. Initial scores ranged from 7.03 to 7.56, with T4 (Watermelon 97% + Mint 2% + Lime 1%) recording the highest score, followed by T5 and T1, while T9 (Watermelon 94% + Mint 3% + Lime 3%) showed the lowest score. Despite the decline during storage, T4 maintained the highest flavour score (7.29) at 45 days and recorded the highest mean flavour score (7.43), followed by T5 and T1. Lower flavour stability was observed in T8 and T9. The reduction in flavour was attributed to oxidative and biochemical changes and the loss of volatile flavour compounds. The results indicated that moderate incorporation of mint and lime improved flavour retention and overall sensory quality during storage.

Overall acceptability:

The overall acceptability of watermelon-mint-lime blended RTS beverages decreased gradually during the 45-day storage period. Initial scores ranged from 7.12 to 7.55, with T4 (Watermelon 97% + Mint 2% + Lime 1%) recording the highest score, followed by T1 and T5, while T9 (Watermelon 94% + Mint 3% + Lime 3%) showed the lowest score. Despite the decline during storage, T4 maintained the highest overall acceptability score (7.32) at 45 days and recorded the highest mean score (7.44), followed by T5 and T1. Lower acceptability was observed in T9, indicating reduced sensory stability. The decline in acceptability was attributed to flavour loss, colour deterioration and physicochemical changes during storage.

The results showed that moderate incorporation of mint and lime improved sensory quality, consumer acceptability and storage stability of the RTS beverage.

Conclusion

The study demonstrates that blending watermelon juice with moderate levels of mint and lime improves the sensory stability of ready-to-serve (RTS) beverages over 45 days of ambient storage. While natural biochemical degradation caused a gradual decline in all treatments, T4 (Watermelon 97% + Mint 2% + Lime 1%) consistently emerged as the superior formulation. It retained the highest final and mean scores across all parameters: taste (initial 7.40, final 6.80), colour (initial 8.90, final 7.00), appearance (initial 7.53, final 7.34), flavour (initial 7.56, final 7.29) and overall acceptability (initial 7.55, final 7.32). Conversely, the control (T0) suffered severe color degradation (final 4.50) and highadjunct T9 (Watermelon 94% + Mint 3% + Lime 3%) recorded the lowest overall scores (final appearance 6.61). Ultimately, optimizing the beverage with 2% mint and 1% lime (T4) provides a synergistic balance that retards sensory deterioration and maximizes shelf-life.

Acknowledgement

AcknowledgementI express my sincere gratitude to all contributors to the project's successful completion, particularly my Advisory Committee for their guidance and support, my classmates for their cooperation, and the College of Horticulture and Research Station, Sankara, for providing necessary facilities and resources.

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