Volatile Fatty Acids in Laboratory and Field Silage

Division of Agricultural Biochemistry, Department of Biological Chemistry, University of Aberdeen
Journal of the Science of Food and Agriculture (Impact Factor: 1.71). 03/1954; 5(3):120 - 126. DOI: 10.1002/jsfa.2740050302


The results of work conducted on the formation of volatile fatty acids in laboratory slurries of minced crop and water mixtures is presented. The absence of formic acid in such slurries has been noted. The occurrence of acids higher than C6, under varying conditions of temperature, aeration or anaerobiosis, has not been demonstrated. Straight-chain volatile acids from C1 to C8 have been shown to occur in field silage but only occasionally has the presence of branched-chain acids been noted. The principal volatile acid present is acetic acid.

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    ABSTRACT: Results are presented for the composition and digestibilities of the constituents of a medium-protein grass-clover mixture and of molassed and unmolassed silages derived from it. Determinations of soluble sugar and fructosan values have carried out in addition to the usual estimations, and the possible effects of the reduction of soluble carbohydrate resulting from fermentation during ensilage, on the nutritional value of the silage product, have been discussed. The losses of fresh material, dry matter and nitrogen which have been observed were exceptionally low compared with the losses generally reported for this type of experiment, and, for both types of silage, weights of lactic and lower fatty acids have been found considerably in excess of the equivalent soluble carbohydrate losses. Little difference in quality and feeding value has been observed between molassed and ordinary silage at a crude protein level of 12–13% dry matter and both types of silage compared very favourably with the original grass.
    No preview · Article · Mar 1956 · Journal of the Science of Food and Agriculture
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    ABSTRACT: The more abundant of the non-nitrogenous non-volatile organic acids in extracts of perennial rye-grass are quinic, malic and citric. Succinic acid and others are present in small amount. An investigation of changes taking place during ensilage and other conservation processes is described, lactic acid and the volatile fatty acids being determined simultaneously. In silage there is rapid and complete disappearance of malic and citric acid; this is also noted to a lesser extent during wilting and drying whereas, in grass preserved with metabisulphite, there is loss of malic acid alone.
    No preview · Article · Dec 1957 · Journal of the Science of Food and Agriculture
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    ABSTRACT: A method is described for the separation of butyric, propionic, acetic, formic, succinic and lactic acids from silage extracts by chromatography on columns of silica gel eluted with mixtures of benzene and n-butanol. Separated acids were estimated by titration with barium hydroxide solution. The method has been applied to silages made from pure species of herbages at different stages of growth and receiving different treatments before ensilage. Lactic acid concentrations up to 11.5% of the dry matter were recorded, giving rise to low pH values. Butyric acid concentrations of up to 5% raised the pH and under these conditions only small amounts of lactic acid were present; propionic acid concentrations rose to 1–2% in some cases and trace amounts of formic acid could be detected. Acetic acid was present in all silages at concentrations of up to 7% of the dry matter, and appeared to fall off as the nitrogen content of the crop decreased. As the herbage matured, the total acid concentration of the silage decreased.
    No preview · Article · Apr 1964 · Journal of the Science of Food and Agriculture
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