Short communication: Stabilization of milk proteins at pH 5.5 using pectic polysaccharides derived from potato tubers

摘要

Potato pectin has unique molecular characteristicsthat differentiate it from commercially available pectinssourced from citrus peels or apple pomace, including ahigher degree of branching and a higher acetyl content.The objective of this study was to evaluate the abilityof potato pectin to stabilize milk proteins at an acidicpH above their isoelectric point, pH 5.5, at which nocitrus- or apple-derived pectins are functional. Potatopectin was extracted from raw potato tubers by heatingat pH 4.5 and 120°C for 30 min after removing starchsolubilized using a dilute HCl solution adjusted to pH2. The potato pectin was found to have a galacturonicacid content of 17.31 ± 3.29% (wt/wt) and a degree ofacetylation of 20.20 ± 0.12%. A portion of the potatopectin was deacetylated by heating it in an alkalinecondition. The deacetylation resulted in a galacturonicacid content of 19.12 ± 4.64% (wt/wt) and a degree ofacetylation of 3.03 ± 0.03%. Particle size distributionsin acidified milk drink (AMD) samples adjusted to pH5.5 demonstrated that the acetylated and deacetylatedpotato pectins were capable of inhibiting the aggregationof milk proteins to the largest degree at a pectinconcentration of 1.0 and 0.25% (wt/wt), respectively.Pectin molecules that were not bound to milk proteinsin these AMD samples were quantified after centrifugallyseparating milk proteins and pectin bound tothem from the serum. We found that, for the acetylatedand deacetylated potato pectins, all or approximatelyhalf of the pectin molecules were bound to milk proteinsat a pectin concentration of 0.25 or 1.0% (wt/wt),respectively. These results suggest that the presence ofacetyl groups is a critical factor that determines howpotato pectin molecules bind electrostatically to milkprotein surfaces, form 3-dimensional structures there,and function as a stabilizer. The present results demonstratethat potato pectin can stabilize milk proteins atpH 5.5 and potentially enable the development of novelAMD products with improved functionality for caseincontainingproducts with moderately acidic pH profiles.