The solubility of potato proteins from industrial potato fruit juice as influenced by pH and various additives

Abstract

The effects of pH and various additives on the precipitation and (re)solubility at pH 7 of potato proteins from industrial potato fruit juice (PFJ) were studied. The use of various strong and weak acids did not result in differences in protein precipitation, which on average occurred to a maximum of 60% of total protein at pH 3. Weak acids did, however, result in precipitates with a higher resolubility at pH 7 compared with strong acids. At pH 5, addition of FeCl 3 or ZnCl 2 increased both precipitation and resolubility compared with the situation without additives. The largest increases in both precipitation and resolubility were achieved using organic solvents at pH 5 as an additive, resulting in a maximum precipitation and maximum resolubility at pH 7 of 91 and 83% of total protein respectively. The results described in this study lead to the hypothesis that precipitation and resolubilisation of potato proteins from PFJ are not determined by their isoelectric pH but by their interactions with low-molecular-weight components.

Patatin, the major protein of potato (Solanum tuberosum L.) tubers, and its occurrence as genotype effect: processing versus table potatoes

“…The processing genotypes are characterised by a longer growing season, and high a starch concentration; the tuber protein was considered to be an unwanted by-product of the starch production rather than a valuable raw material for further processing. However, because of the above mentioned nutritional and biochemical potential of potato tuber proteins and especially patatin (Strickland et al 1995;Macrae et al 1998;Ralet & Guéguen 2000;Tonón et al 2001;Åhman & Melander 2003;Wang & Xiong 2005), efforts exist to isolate tuber proteins from potato fruit water for utilisation in feed, food, and biotechnological applications (Straetkvern et al 1999;Koningsveld et al 2001). Information describing the genotype and annual stability of patatin presence in potato tubers as well as correlations between patatin abundance and the selected characteristics (tubers size, pure protein content, starch content), is basic for the production and future utilisation of this protein component in various branches.…”

Processing, Valorization and Application of Bio-Waste Derived Compounds from Potato, Tomato, Olive and Cereals: A Review

“…The ultrafiltration with a subsequent diafiltration is more promising because proteins with a higher quality can be manufactured and yields up to 50% arise. Unfortunately, these techniques are limited by the occurrence of membrane fouling at large scale processing and the presence of antinutritional factors like protease inhibitors or glycoalkaloids [119,121,133,135]. Additionally, protein extraction of potato fruit juice under non-denaturating conditions was described in literature: the first step is concentrating the protein by disc stack centrifugation, followed by ultrafiltration, diafiltration and optionally freeze-drying [134].…”

“…Disadvantages of the adsorption procedure are high amounts of protease inhibitors which occur in the protein concentrates. Moreover, the adsorbent has to be removed prior food application [135]. An alternative to heat coagulation is the precipitation at an acidic pH values.…”

“…Several methods were tested and citric acid as well as ferric chloride was identified as most suitable leading to soluble protein precipitates [122,[138][139][140]. Another study examined the influence of various additives on the solubility of proteins from potato fruit juice and figured out that the addition of FeCl 3 , ZnCl 2 and organic solvents (methanol, ethanol, isopropanol) increased the precipitation and resolubility [135].…”

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

“…High energy costs induced by the recovery procedures charge the economy of potato starch production [7]. On the other hand, isoelectric precipitation is a method that can simply and efficiently recover protein from a large quantity of wastewater [8]. In addition, isoelectric precipitation is potentially less damaging to protein quality than heat coagulation.…”