Advances in physicochemical and functional characterization of Prosopis alba exuded gum for its potential application in food industry

VASILE, FRANCO; JUDIS, MARÍA ALICIA; MAZZOBRE, MARÍA FLORENCIA

Pirassununga, Sao Paulo

Workshop; Advances in Molecular Structuring of Food Materials; 2013

School of Advanced Sciences, Faculty of Animal Science and Food Engineering

Under environmental stress conditions, the tree Prosopis alba known in Argentine as “algarrobo blanco” secretes a soluble polysaccharide with characteristics similar to those of arabic gum (AG). This has supported the possibility to use this currently wasted resource, as an effective AG substitute for the encapsulation of sensitive food ingredients. The aim of this study was to investigate the structural characteristics of the Prosopis alba exuded gum (ALG) by monitoring the composition, physicochemical and functional properties. For this purpose, gum tears were dissolved in distilled water at 75°C. The resulting solution was clarified by filtration, dialyzed (10 kDa MWCO), frozen at -18°C and finally freeze-dried. The sample was subjected to commonly referenced characterization tests and compared with those reported for AG. The ALG presented a protein content (7.21±0.062% db) higher than the AG (2.2±0.3% db). The tannin content (0.2±0.01% db), recognized as a toxicity parameter, was lower than those found in the literature for botanically related species. The total polyphenol content was determined in ALG (17.52±0.2 mg eq.tannic acid/g dry solid) and this was satisfactorily correlated with its antioxidant activity, measured in terms of capability to capture the ABTS radical (EC50=0.92±0.03 mg dry solid). In addition, the ALG moisture sorption isotherm was obtained. GAB model resulted the most suited to describe ALG behavior (EPP <0.1%). Thermal transitions were determined by differential scanning calorimetry (DSC), for the systems equilibrated at different aw values (0,11-0,96). Glass transition temperature (Tg) decreased with increasing water content and this plasticizer effect was successfully correlated with the Gordon-Taylor equation. The ALG kGT constant (5.1±0.23), was significantly higher than the reported for AG (2.0±0.3) indicating a greater ALG susceptibility to plasticization by water. ALG exhibit chemical, thermal and sorption properties similar to those of AG, which could be explained in terms of structural and functional groups common to both biopolymers. The physicochemical characterization of ALG is an important aspect to evaluate its potential application in the food industry with the added benefit of leverage an untapped indigenous resource.