Galactooligosaccharides (GOSs) are prebiotics that have been shown to reduce colon cancer risk and enhance immunity. The GOSs can be formed enzymatically from whey lactose using β-galactosidase, but commercial application has been limited. Free-and immobilized-enzyme recycle batch processes were investigated and compared in this study. Optimum initial conditions were estimated using batch solutions. Using these optimum conditions, an ultrafiltration (UF) free-enzyme system was developed, and UF fluid pressure (100 to 400 p.s.i.) effect on enzyme performance was studied and compared with a 0 p.s.i. batch control. The optimum conditions were also used to develop an immobilized-enzyme process using polyethyleneimine (PEI), glutaraldehyde (GA), and cotton cloth. The PEI and GA immobilized agents were studied for their effect on enzyme inactivation. Finally, compatible free-and immobilized-enzyme recycle batch systems were compared for GOS production. Optimum initial enzyme conditions were estimated as 270 g/L initial lactose, 4.5 g/L initial enzyme (Aspergillus oryzae, 9400 U/g), and 30-min incubation. Fluid pressure within the free-enzyme UF membrane system had no significant effect on enzyme performance. The highly agitated UF enzyme system was found to be superior to the less agitated 0 p.s.i batch control. In the immobilization process, approximately 50% to approximately 90% enzyme inactivation was found with the combination of PEI and GA. Equivalent free-and immobilized-enzyme systems showed very similar maximum GOS production of approximately 22% and approximately 20% (w/v) at approximately 15 to 17 min, or 50% conversion for free-and immobilized-systems, respectively.

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No abstract

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.