Recovery of presumptive Alicyclobacillus strains from orange fruit surfacest.

Objectives of this research were to investigate the detection frequency of presumptive Alicyclobacillus strains, also known as thermoacidophilic or acidothermophilic bacteria, on oranges entering juice-processing facilities and to compare results from three common isolation agars (acidified potato dextrose agar, Ali agar, and K agar). A total of 1,575 fruits were sampled from three points (ungraded fruits, graded sound fruits, and graded defective fruits) at two juice-processing facilities during two harvest seasons. Buffer used to rinse individual fruits was assayed for the presence of thermoacidophilic bacteria using an enrichment procedure. Isolates were considered presumptive Alicyclobacillus if they were gram-positive, sporogenous, rod-shaped bacteria, with growth at 45 degrees C and no or slight growth at 25 degrees C on a low pH medium (pH 3.7) coupled with lack of growth on a neutral pH medium (pH 7.0) at both temperatures and a lack of growth in Sulfobacillus broth medium (pH 2.0). More than one third of all fruits sampled at the two facilities were contaminated with presumptive Alicyclobacillus strains. Therefore, incoming fruits are a substantial means by which these organisms gain entrance to the processing facility. Significantly (P < or = 0.05) more detection was observed with a mineral-containing medium (Ali agar) than with nonmineral containing media (K agar and acidified potato dextrose agar).

Capillary electrophoresis and high-performance liquid chromatography determination of polyglutamyl 5-methyltetrahydrofolate forms in citrus products.

The 5-methyltetrahydrofolate (5mTHF) polyglutamates in citrus products were analyzed by capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). Folate species were purified from citrus products and concentrated from 2- to 100-fold using combined folate-affinity chromatography and C18 extraction. Seven polyglutamyl 5mTHFs were found in most not-from-concentrate (NFC) orange juices (OJ) in total amounts of approximately 1 nmol/mL, with varying distributions of individual polyglutamates. Folate amounts and distributions were also measured in orange fractions, single-strength OJ from concentrate, NFC grapefruit juice, and citrus peel molasses. Models containing ascorbic acid had folate thermal degradation rates one-seventh that of models without ascorbic acid. Pasteurization studies demonstrated that folate loss was <2% for commercial OJ pasteurization conditions (i.e., 93 degrees C for 5 s, 88 degrees C for 15 s, and 82 degrees C for 30 s). Both methods were precise, reproducible, and potentially faster than traditional analytical procedures requiring enzymatic deconjugation and microbial assays.

Yeast species associated with orange juice: evaluation of different identification methods.

Five different methods were used to identify yeast isolates from a variety of citrus juice sources. A total of 99 strains, including reference strains, were identified using a partial sequence of the 26S rRNA gene, restriction pattern analysis of the internal transcribed spacer region (5.8S-ITS), classical methodology, the RapID Yeast Plus system, and API 20C AUX. Twenty-three different species were identified representing 11 different genera. Distribution of the species was considerably different depending on the type of sample. Fourteen different species were identified from pasteurized single-strength orange juice that had been contaminated after pasteurization (PSOJ), while only six species were isolated from fresh-squeezed, unpasteurized orange juice (FSOJ). Among PSOJ isolates, Candida intermedia and Candida parapsilosis were the predominant species. Hanseniaspora occidentalis and Hanseniaspora uvarum represented up to 73% of total FSOJ isolates. Partial sequence of the 26S rRNA gene yielded the best results in terms of correct identification, followed by classical techniques and 5.8S-ITS analysis. The commercial identification kits RapID Yeast Plus system and API 20C AUX were able to correctly identify only 35 and 13% of the isolates, respectively. Six new 5.8S-ITS profiles were described, corresponding to Clavispora lusitaniae, Geotrichum citri-aurantii, H. occidentalis, H. vineae, Pichia fermentans, and Saccharomycopsis crataegensis. With the addition of these new profiles to the existing database, the use of 5.8S-ITS sequence became the best tool for rapid and accurate identification of yeast isolates from orange juice.