Effect of culture conditions on production of butter flavor compounds by Pediococcus pentosaceus and Lactobacillus acidophilus in semisolid maize-based cultures.

Two series of 120 h mixed cultures of Pediococcus pentosaceus MITJ-10 and Lactobacillus acidophilus Hansen 1748 were grown in semisolid maize-based media, applying an orthogonal factorial design in order to establish the most adequate parameters to get compounds related to butter-like flavor. Conditions of maize pre-treatment established in the first series were hot lime-treatment for 20 min, grinding and sieving to 0.0165 in., partial defatting and cooking for 25 min. While the culture conditions established for the second series were the addition of yeast extract (0.2% w/w), and culture starting with 2x10(6) CFU g(-1) and a ratio of P. pentosaceus and L. acidophilus, 3:1. The fermentation profile was studied in a last culture. Lactic acid bacteria (LAB) prevailed over the native microorganisms, with a specific growth rate of 0.47 h(-1). Diacetyl production correlated (r2=0.9972) with the 12 h exponential growth phase of LAB. The concentration of diacetyl at that time was 779.56 mg kg(-1). The contents of lactic acid and volatile fatty acids were low at 12 h, 665 and 1312 mg kg(-1), respectively. During the long stationary phase, they increased up to 4800 and 1886 mg kg(-1), respectively. This procedure might be useful to prepare naturally aromatized raw materials for the food industry.

Diacetyl formation by lactic bacteria

Los aromas o sustancias aromatizantes son compuestos intermediarios empleados ampliamente en la industria alimentaria. Estos aditivos pueden ser producidos por síntesis química o naturalmente por fermentación. Ultimamente los más solicitados por los industriales debido a la tendencia que tienen los consumidores hacia los productos naturales son los producidos por fermentación. El diacetilo es uno de los componentes primordiales del aroma a mantequilla, aunque también deben estar presentes otros compuestos como la acetoína, el acetaldehído y el 2,3-butanodiol en menor proporción. La mezcla de todos estos compuestos en proporciones adecuadas es lo que origina el aroma característico a mantequilla. El diacetilo, así como los compuestos de acompañamiento son producidos por la fermentación de las bacterias lácticas. La ruta metabólica del piruvato. En este caso la biosíntesis del diacetilo depende de la presencia de citrato en el medio. Otra ruta alternativa es a partir del acetaldehído, en esta ruta parece que no interviene el citrato. En este trabajo se hace una revisión de los mecanismos de formación del diacetilo por bacterias lácticas; así como de los factores más importantes que influyen en la biosíntesis de este metabolito

Diacetyl formation by lactic bacteria.

Some of the most widely used products in the food industry are flavour compounds. These products can be obtained either by chemical synthesis and therefore are called synthetic or by fermentation thus called natural flavors. There is a tendency towards the use of natural products by the consumer, therefore there is an increasing industrial interest in them. One of these products is diacetyl, an important component in the flavor of butter, although others, like acetoin, acetaldehyde and 2,3-butanediol play a role in the flavor, they are present in trace amounts. The mixture of all these compounds produced during the lactic acid fermentation in suitable proportions is what gives butter its characteristic flavor. The most common metabolic route that produces diacetyl is the one starting from pyruvate, in this case it seems that the biosynthesis is related to the presence of citrate in the medium. An alternative route for the production is from acetaldehyde, in this route citrate does not seem to intervene. In the present paper a review of the mechanisms of formation of diacetyl by lactic acid bacteria, as well as the most important factors that influence the biosynthesis of this metabolite is made.