High pressure processing of spoilage fungi as affected by water activity in a diluted apple juice concentrate

Publication date: Available online 19 July 2019Source: Food ControlAuthor(s): Elizabeth C. Buerman, Randy W. Worobo, Olga I. Padilla-ZakourAbstractHigh Pressure Processing (HPP) is a method used to extend shelf life of foods by subjecting products in their final packaging to extreme pressure. This leads to protein degradation in microbial cells, membrane degradation, and eventual cell death. Survival of spoilage organisms, especially spore-formers, has not been closely considered in regard to the effect of water activity (aw). The purpose of this study was to determine the effect of pH and aw on HPP apple juice to prevent fungal spoilage during shelf life.Apple juice concentrate was adjusted to aw 0.94 (39.3°Brix), 0.96 (32.2°Brix), 0.98 (22.0°Brix), or 1.00 (7.1°Brix) and pH 4.6 or pH 7.0. Polyethylene terephthalate bottles were filled with concentrate and inoculated with Penicillium spp., Aspergillus niger, Byssochlamys spectabilis, Rhodotorula mucilaginosa, Candida parapsilosis, Torulaspora delbrueckii, or Brettanomyces bruxellensis. Samples were HPP treated at 450 MPa for 1.5 min and for pressure-resistant species, at 600 MPa for 1.5 min or 3 min to resemble industrial processing conditions. Fungi were more resistant to HPP at lower aw and higher pH. C. parapsilosis was more resistant to HPP than the other organisms tested. Fungi, with the exception of C. parapsilosis, experienced a 4.26- or greater log reduction at aw of 0.98 and above at either pH. Their r...
Source: Food Control - Category: Food Science Source Type: research