353. ‘Malty’ flavour in starter and butter

Abstract

One of the most troublesome defects occurring in fresh butter is the so-called malty flavour, which was formerly quite common. It usually first appears in the starter and is transferred to the butter during churning. 'Malty* flavour is caused by micro-organisms. Weigmann(i) in 1899 was the first to show that malty flavour is due to micro-organisms and to isolate an organism which produced a marked malty flavour. He reports: 'Der Geruch ist so intensiv, dass er sich nicht nur ganz und gar auf die Butter iibertragt, sondern auch in die Luft des Aufbewahrungsraumes iibertragt.' After cultivation on agar for 4 years the organism still produced the malty flavour. Sadler (2) described an organism, isolated from milk, which produced a caramel flavour before coagulation of the milk. This flavour may be identical with the malty flavour. Sadler's organism resembled Str. lactis. In another paper Sadler (3) described a coccus which produced a caramel odour and fermented the same sugars as Str. lactis. The source of the taste and odour were not determined. Hammer with his collaborators (4,5) considers the organism to be identical with a strain of Str. lactis which he described, and suggested the name Str. lactis var. maltigenes. Weigmann(6), however, considers that the malty flavour is formed by degenerated lactic acid bacteria. Sadler(7), in 1928, published an investigation in which he claims that the malty aroma-producing substance is ethersoluble.In the same year Kelly (8) reported on four diplococci producing a caramel taste. Their behaviour in different sugars was not uniform, and two of them fermented arabinose, raffinose and starch, but not dextrin. Nevertheless, the author regards them as Str. lactis var. maltigenes, since they coagulate milk rapidly and resemble Str. lactis in their morphology and ability to ferment sugars and alcohols. Leitch(9) mentions that the organism producing malty flavour appears in the milk of certain cows.Heucke(iO) describes malty flavour-producing diplococci which never grow in chains. He failed to find them in green plants, but frequently in malts and sometimes in butter and soil. In milk they appeared to be more common in winter than in summer. They coagulated milk even at relatively low temperatures (6-8° C). Heucke regards them as members of the Str. lactis group and states that the ability of bacteria to develop malty flavour is not impaired by continued cultivation in the laboratory. He also claims that the flavour is produced from lactic acid and from all the sugars and alcohols fermentable by Str. lactis. Stocker(ii) has isolated from milk, starter and butter several species of bacteria producing malty flavour, and he regards them as species of Str. lactis. He assumes the malty flavour to arise from casein.In addition to bacteria of the Str. lactis type other micro-organisms have been found to form aroma substances of this kind. Thus Baumann (12) reports the isolation of two species of Str. faecium and two species of Str-. bovis which cause a disagreeable malty smell and taste in ...