Heat Resistance of Juice Spoilage Microorganisms

Abstract

The heat resistance of various yeasts (Saccharomyces cerevisiae, Rhodotorula mucilaginosa, Torulaspora delbrueckii, and Zygosaccharomyces rouxii), molds (Penicillium citrinum, Penicillium roquefortii, and Aspergillus niger), and lactic acid bacteria (Lactobacillus fermentum and Lactobacillus plantarum) obtained from spoiled acid or acidified food products was determined in 0.1 M citrate buffer at pH values of 3.0, 3.5, and 4.0. S. cerevisiae was the most heat resistant of the microorganisms in citrate buffer, and its heat resistance was further evaluated in apple, grapefruit, calcium-fortified apple, and tomato juices as well as in a juice base with high fructose corn syrup. Decimal reduction times (D-values) and changes in temperature required to change the D-value (z-values) for S. cerevisiae were higher in the juices than in citrate buffer at all pH values tested. The D57 degrees C(135 degrees F)-values varied from 9.4 min in the juice product with pH 2.8 to 32 min in a calcium-added apple juice with pH 3.9. The S. cerevisiae strain used in this study can be used in thermal-death-time experiments in acidic products to calculate process conditions and in challenge tests to validate the calculated temperatures and hold times during processing.

Microbial Inactivation and Physicochemical Properties of Ultrasound Processed Pomegranate Juice

“…Ryu and Beuchat (48) reported increased heat resistance in acid-adapted E. coli 0157:H7 in heat-treated fruit juices. Shearer et al (51) reported that the heat resistance of S. cerevisiae obtained from spoiled acidic products was higher in fruit juices than in citrate buffer. Increased resistance to organic acids, which are used as preservatives, after weak acid adaptation was reported in S. cerevisiae (44,65).…”

Inactivation of Escherichia coli O157:H7 and spoilage yeasts in germicidal UV-C-irradiated and heat-treated clear apple juice

“…When suspended in a strawberry-based medium, D. hansenii cultivated in a liquid growth medium was also found to be less heat resistant than its S. cerevisiae counterpart (TruongMeyer, Strehaiano, & Riba, 1997). Furthermore, S. cerevisiae was similarly established to be more heat resistant compared to a number of juice spoilage yeasts (T. delbrueckii, Rhodotorula mucilaginosa, Zygosaccharomyces rouxii), molds (Penicillium roquefortii, Aspergellus niger) and lactic acid bacteria (Lactobacillus fermentum, Lactobacillus plantarum); and was identified as an appropriate challenge organism in establishing thermal processes for acidic products (Shearer, Mazzotta, Chuyate, & Gombas, 2002). The heat inactivation rate of the composite yeast species was greater than most of the yeasts but was 4 times smaller than that of S. cerevisiae.…”

Sonication-assisted preparation of CaO nanoparticles for antibacterial agents

“…13 This feature allows L. plantarum to grow easily in juice drinks. 14 In fact, it may metabolize citric and malic acids present in fruit juices and fruit drinks, reducing the acidity of the product.…”