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High-Resolution NMR Detection of Cholesterol Oxides in Spray-Dried Egg Yolk (1992)

FONTANA, A. ; ANTONIAZZI, F. ; CIMINO, G. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Journal of food science 57 (1992), S. 0

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ISSN: 1750-3841

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology

Notes: A new approach, alternative to currently available methods, for studying cholesterol oxidation in egg powder is reported. The quantitative analysis of cholesterol oxides was carried out by high-resolution proton nuclear magnetic resonance (1H-NMR). The following oxides were isolated from spray-dried egg powder by rapid chromatographic procedures and detected by selecting “marker”1H-NMR signals: 7-ke-tocholesterol, 7α-hydroxy-cholesterol, 7β-hydroxy-cholesterol, cholesterol-α-epoxide and cholesterol-β-epoxide. The quantified cholesterol derivatives ranged from 4.9 to 9.1 ppm with a detection limit of 0.3 ppm (5 μ.g from 16g of matrix). The main usefulness of the method should be in investigating intermediates and products due to chemical transformation of cholesterol during storage and heating of foodstuffs.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2621.1992.tb14312.x

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Continuous alcoholic fermentation of sucrose using flocculating yeast. The limits of invertase activity (1992)

Fontana, A. ; Ghommidh, C. ; Guiraud, J. P. ; [et al.]

Springer

Biotechnology letters 14 (1992), S. 505-510

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ISSN: 1573-6776

Source: Springer Online Journal Archives 1860-2000

Topics: Process Engineering, Biotechnology, Nutrition Technology

Notes: Summary At high flow rates, the continuous alcoholic fermentation of sucrose in a laboratory fermenter with internal cell recycle, using a strongly flocculating yeast can be limited by the substrate hydrolysis. This system is sensitive to glucose catabolic repression and to mineral deficiency. The release of invertase activity in the medium is negligible. From theoretical and experimental considerations, the hydrolysis rate is imposed by diffusionnal limitations in the biomass particles. Nevertheless, ethanol productivities as high as 68 g/L.h can be reached, without biomass retention problems. A better understanding of the basic phenomena involved in floc formation and evolution is required to control reactor performances.