Foamability and Foam Stability of Male and Female Date Palm Sap (Phoenix dactylifera L.) During the Collection Period

This work aimed to study the influence of date palm sex on the surface properties of date palm sap (DPS) (Phoenix dactylifera L.) during the collection period. The behavior at the interface and foaming properties were evaluated via equilibrium surface tension (drop volume) and bubbling method, respectively. Unlike male sap, the female sap was unable to produce foam due to its low rate of adsorption, low average hydrophobicity values, and low bulk viscosity values throughout the collection period. For male sap, there are significant differences (p<0.05) on foaming properties throughout the collection period. In fact, the last 3 weeks of sap collection were characterized by a decrease pace of surface tension which explains the enhancement of both foam capacity and stability. The last week of collection period present the best foam power (0.9). To explain these differences, the interactions of several factors and their affects on foaming properties were examined. Results showed a positive correlation between foam capacity and average hydrophobicity values. In the other hand, foam stability exhibits a positive correlation with the increase of protein concentration and bulk viscosity.