Blends of Cactus Cladode Powder with Corn Starch, Milk Proteins and Gelatin: Rheological Evaluation and Application to a Soup Model

Abstract

Cactus cladodes (Opuntia ficus-indica) is a valuable source of dietary fibers. In this study, peeled cladode powder was produced by air drying at 40 °C and was characterized for its color, dietary fiber content, and rheological behavior. Cladode powder aqueous suspensions of 3% w/w were prepared and the effect of protein (gelatin, sodium caseinate, and whey protein) or salts (NaCl/CaCl2) on the blend’s viscosity was investigated. Additionally, cladode powder was incorporated in a soup model, aiming at substituting corn starch. Our powder had an appealing green color, but its deterioration was fast when it was exposed to light. A shear-thinning behavior was observed in all cladode-protein mixtures, but viscosity values depended considerably on the protein type and the pH values. Notably, gelatin addition led to higher apparent viscosity of cladode powder at pH 6, suggesting interactions with cladode mucilage, but this effect was reversed at pH 4, below gelatin isoelectric point. The Ostwald-de Waele model successfully correlated viscosity-shear rates data, whereas the Casson model presented a good fit mainly in starch containing systems. Corn starch substitution by cladode powder, in the soup model, led to lower consistency coefficient values. In soups, the logarithmic mixing law was applied at different corn starch: cladode powder ratios to highlight their possible interactions. The values obtained diverged slightly downwards from the logarithmic mixing law. When purified mucilage was added—instead of cladode powder—the samples diverged slightly upwards from the logarithmic mixing law.