Properties of Whey Protein Concentrate Prepared by Heating Under Acidic Conditions

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Abstract
A highly soluble whey protein concentrate was prepared by adjusting the pH of sweet whey to 2.5-3.5 and heating at 90.degree. C for 15 min. Upon cooling the pH was adjusted to 4.5 and the precipitated protein removed by centrifugation. The precipitate then was neutralized to pH 6.0 and spray dried. Recoveries of total protein ranged from 63-74% and from 35-53% for whey heated in the pH range of 2.5-3.5 with and without added Fe (30 mg/l). Whey protein concentrate prepared by heating at pH 2.5-3.0 had a minimum solubility of 78%. This was reduced to 51% when the pH during heating was 3.5. Although addition of Fe to whole whey increased protein recovery, solubility was reduced. Concentrating whey prior to heating greatly increased protein recovery but substantially reduced solubility. The viscosity of spray-dried samples of acid-heat whey protein concentrate reconstituted to 33% solids ranged from 4000-36,800 centipoise while commercial samples had viscosities of 400-1840 centipoise. Experimental samples of whey protein concentrate gelled at protein concentrations of 2, 4, 6 and 8% heating at 95.degree. C for 20 min. All experimental samples had excellent color stability while commercial samples darkened upon heating.