Effects of pH and Heat Treatments on the Structure and Solubility of Potato Proteins in Different Preparations

Abstract

The soluble potato proteins are mainly composed of patatin and protease inhibitors. Using DSC and both far-UV and near-UV CD spectroscopy, it was shown that potato proteins unfold between 55 and 75 degrees C. Increasing the ionic strength from 15 to 200 mM generally caused an increase in denaturation temperature. It was concluded that either the dimeric protein patatin unfolds in its monomeric state or its monomers are loosely associated and unfold independently. Thermal unfolding of the protease inhibitors was correlated with a decrease in protease inhibitor activities and resulted in an ionic strength dependent loss of protein solubility. Potato proteins were soluble at neutral and strongly acidic pH values. The tertiary structure of patatin was irreversibly altered by precipitation at pH 5. At mildly acidic pH the overall potato protein solubility was dependent on ionic strength and the presence of unfolded patatin.

Influence of high isostatic pressure on structural and functional characteristics of potato protein

“…Differences in comparison to samples made of protein concentrate can be explained by the higher purity of the commercial isolate. No precipitation of isolated patatin after exposure to temperatures up to 90°C was also reported by Pots, De Jongh, Gruppen, Hamer, et al (1998), whereas heating of potato fruit juice led to a strong decrease in solubility at temperatures exceeding 60°C (van Koningsveld et al, 2001). Protein-protein interactions between patatin and the protease inhibitor fraction might result in large aggregates not formed in pure patatin solutions.…”

“…Solubility changes reported after heating of patatin at ionic strengths of 200 mM were similar to those of potato fruit juice, whereas patatin remained into solution at 15 mM ionic strength (van Koningsveld et al, 2001). According to the Smoluchowski-Fuchsmechanism, the retardation between particles decreases with increasing ionic strength and interactions between particles promoting the formation of large aggregates are favored (Pots, ten Grotenhuis, Gruppen, Voragen, & de Kruif, 1999).…”

Amino acid composition of enzymatically hydrolysed potato protein preparations

“…In terms of ash content, all studied isolates displayed its low amounts (not more than 1.98% found in PIV). According to some authors (van Koningsveld et al 2001;Miedzianka et al 2012) conducting the thermal coagulation of protein contained in potato juice at increased ionic strength by means of salt addition has several advantages. First of all, it ensures a high protein yield and decreases the temperature of coagulation to 65-70°C.…”

“…high temperature, usually exceeding 90°C, and low pH -in the range of 4-5. On a laboratory scale, potato proteins have been isolated by means of thermal coagulation at varying pH, room temperature and in the presence of HCl, H 2 SO 4 , FeCl 3 , Al 2 (SO 4 ) 3 , citric acid or by salting out with (NH 4 ) 2 SO 4 (Ralet & Guéguen 2000;van Koningsveld et al 2001). However, intense heat-coagulation results in complete denaturation of the protein and it also significantly diminishes its functionality (PĘksa et al 2009) as well as digestibility.…”

Utilization of Potato Protein Recovered from Wastewater of Potato Starch Factory as Cattle Feed

“…Potato protein is of relatively high nutritional quality-comparable to that of whole egg-and therefore it has high potential for use in food products for mammals [11,12]. In 2013, the prices of soybeans, wheat and corn have all soared to 1.7 to 2.6 times their levels in 2006.…”