The structural characteristics and rheological properties of Lebanese locust bean gum

• An important effect of temperature, stress, and concentration on the behavior of LBGs.
• Lebanese LBGs exhibited non-Newtonian behavior at a concentration of 1% (w/v).
• A shifting in the rheological profile was shown between populations.
• Rheological properties were related to galactomannan content, molecular weight, or diversity in geographical origin.

To characterize and study the rheological behavior of Lebanese locust bean gum (LBG), nine Lebanese carob varieties, including a wild type, were randomly collected from various sites and different altitudes of the Lebanese territories. After an extraction and purification (pLBG) step, the obtained locust bean gum was submitted to several physic-chemicals (size distribution, charge and macromolecular weight) and rheological characterization in a wide range of temperature (25–55 °C). The obtained results showed that the gum yield (40–60%), the charge (−2.67 to −12.95), the size (56.37–92.23 nm), the weight–average molecular weight (535–826 kDa) and intrinsic viscosity [η] (7.25–10.76 dl/g) vary significantly depending upon the variety and the geographical localization. However, principal component analysis (PCA) indicated that the size and molecular weight are the most distinctive variables. The rheological investigation indicated that pLBG exhibit Newtonian flow behavior at a concentration less or equal to 0.1% (w/v) and shear-thinning behavior for higher concentrations (0.5–2%). The effect of temperature on flow behavior was well fitted by Ostwald–de Waele model (power law model) and the flow behavior index (n) was less than 1 for all studied varieties; which means that LBGs had a pseudo-plastic flow. The all new knowledge obtained in this study on the Lebanese locust bean gum will open to these interesting macromolecules new niches in food and cosmetics applications.