Investigating ingredient influence on reconstitution of powdered cocoa beverage via constrained mixture design

Reconstitution of a powdered cocoa beverage (PCB) produced by wet-mixing and oven-drying were studied. Sixteen PCB samples with different proportions of core ingredients, namely cocoa (5–25 %), skimmed milk (10–50 %), hydrolysed cereal extract (15–60 %), sucrose (0–30 %) and palm olein (0–15 %), were generated via a constrained mixture design. PCB samples had varying physical properties which included bulk porosity (57.3–74.8 %), particle surface hydrophilicity (contact angle = 60.0–94.5°) and glass transition temperature (51.2–86.3 °C). Consequently, PCB samples differed in reconstitution properties like wetting time (11–>300 s), reconstitution time (14–141 s) and soluble content (51.3–86.8 %). Subsequently, mixture regression models were developed to varying success (adjusted R² = 70–97 %) for identifying the influence of each core ingredient on physical and reconstitution properties of PCB. PCB wettability was most improved by increasing the proportion of hydrolysed cereal extract, through forming powders with moderate particle surface hydrophilicities but higher glass transition temperatures and higher bulk porosities. Conversely, PCB wettability became exceptionally poor when it contained >35 % skimmed milk and <5 % palm olein. Additionally, a higher ratio of protein-rich skimmed milk against carbohydrate-rich hydrolysed cereal extract and sucrose led to solubility loss in PCB.