Development, RSM-guided optimisation, and comprehensive physicochemical characterisation of a novel functional smoothie fortified with carrot-beetroot juice and bioactive seeds

Abstract:

Rising consumer demand for nutrient-dense, minimally processed functional beverages has catalysed interest in formulations that synergistically combine phytochemical-rich vegetables with bioactive seeds. This study reports the first comprehensive development, statistical optimisation, and multi-attribute physicochemical characterisation of a novel functional smoothie incorporating carrot-beetroot juice and bioactive seeds (chia and flax). A five-factor Box-Behnken Design (BBD) under Response Surface Methodology (RSM) was employed, varying carrot juice (50-75 ml), beetroot juice (50-75 ml), water (25-50 ml), chia seeds (2-5 g), and flaxseeds (2-5 g) across 46 experimental runs evaluated for overall acceptability (OA) by a hedonic panel (n = 10). The quadratic model exhibited excellent statistical adequacy (F-value = 17.71; p< 0.0001; R² = 0.93; adjusted R² = 0.87; adequate precision = 15.70). Carrot juice concentration (A) and water volume (C) exerted the dominant linear influence on OA, while pronounced quadratic terms for all five factors confirmed true optima within the experimental space. Numerical optimisation yielded the desirability-optimal formulation (carrot juice 62.5 ml, beetroot juice 62.5 ml, water 37.5 ml, chia seeds 3.5 g, flaxseeds 3.5 g), validated by a confirmatory OA of 9.23 versus a predicted value of 9.00 (prediction error: 2.56%). Comprehensive characterisation of the optimised smoothie revealed: total phenols 135.33±2.51 mg GAE/kg FW; total carotenoids 50.5±0.02 mg/kg FW; DPPH radical scavenging activity 84±0.02% RSA; ascorbic acid 230±0.03 mg/kg FW; and pseudoplastic rheological behaviour (flow behaviour index n = 0.82±0.03). The product demonstrated microbiological safety at day 0 (TPC 2.26±0.12 log CFU/g) and a refrigerated shelf life of 8 days at 4°C. This study provides a validated, reproducible framework for the concurrent optimisation and functional characterisation of multi-ingredient plant-based beverages, with direct translational relevance for nutraceutical product development.