15B-3 |
Method for yeast determination in fruit juices |
R. M. GOODRICH and J. A. Narciso. Citrus Research & Education Center, Univ. of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850-2299 Common citrus industry practice has been to utilize orange serum agar (OSA) and acidified potato dextrose agar (APDA) to recover and enumerate aciduric bacteria and fungi from citrus products, namely juice. These methods are also commonly used for other fruit juices and purees, including apple, grape and tropical fruits. Industrial collection of this data is important for quality control, troubleshooting, and development of manufacturing and sales specifications. Yeasts such as Saccharomyces cerevisiae and Zygosaccharomyces ssp. cause significant spoilage in fruit juice products, leading to ecomonic loss and consumer dissatisfaction. Their efficient and convenient detection is important, and we have screened various alternative methods to APDA for yeast analysis. The objectives of this study were to verify if OSA with the antibiotic chloramphenicol added (OSAC) was an appropriate alternative to APDA for detection and enumeration of yeasts in citrus and other juices. APDA and OSAC were evaluated for their ability to support the growth of fruit juice spoilage yeasts. Both methods were also evaluated in terms of efficiency (time and convenience) and cost per test. Experiments to ensure that color added for media differentiation did not affect performance of OSAC were also conducted. Our results show that OSAC performs as well or better than APDA for determining and enumerating yeasts in citrus juice. Over a range of known juice spoilage yeasts, growth on OSAC was in general more vigorous and consistent. Apple and grape spoilage yeasts were also readily detected on OSAC. These results show that OSAC is an appropriate media to use in the analytical determination in citrus and other juice products.
Session 15B, Citrus
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