Lactic Acid in the Food Industry

The aim of this chapter is to give a brief and reliable overview of possible uses for lactic acid as additive in the current food industry. The importance of lactic acid in the food industry is apparently linked to microbial activity of certain life forms, in particular lactic acid bacteria. Consequently, fermentative bacteria are commonly employed in the food industry as starter cultures for industrial processing. On the other hand, lactic acid can be also used as food additive in the industry of edible products without the presence of lactic acid bacteria. This option can be extremely useful in various ambits. In spite of the main recommended use for this compound (intended as two optical isomers and the racemic mixture of them) as acidity regulator in many food products, several limitations should be considered in certain situations when speaking of maximum allowed amounts and the exclusive use of one isomer only. In addition, several different additives are chemically derived from lactic acid. For this reason, the application spectrum of lactic acid may be broader than the above-mentioned situation, with correlated exceptions and limitations.

The importance of lactic acid in the food industry is certainly correlated with its peculiar chemical and physical properties. According to the Joint FAO/WHO Food Standards Programme, lactic acid isomers and the racemic mixture can be used as acidity regulator in certain foods with the aim of contrasting certain acid-sensitive microorganisms. As a result, the description of food-related uses of lactic acid should involve also peculiar chemical and physical features. This chapter would give a brief and accurate overview of chemical and physical features of this additive. In addition, the chemical synthetic processes for the production of the so-called milk acid are described. Finally, fermentative pathways and related industrial strategies are discussed.

Since the discovery of lactic acid, this compound has been considered for many significant uses and applications in food, cosmetic, pharmaceutical, and chemical industries. Lactic acid occurs naturally in many edible products and also an important ingredient in the food industry. Also, lactic acid is non-toxic and consequently recognised and classified as ‘Generally Recognized as Safe’ substance by the United States Food and Drug Administration for wide use as an additive in the food industry. The notable range of legally allowed food applications depends on the demonstrated antimicrobial action against pathogens and the concomitant shelf life extension. In addition, this acid can serve as a flavouring substance in many food products such as pickles and fermented milk. This chapter discusses some practical and legally allowed examples of lactic acid uses in the production of fermented vegetables, cheeses, fermented milks, sourdough, fermented meats, and wines.

The aim of this chapter is to give a quick and sufficiently comprehensible overview of the current analytical methods for the quantitative and qualitative determination of lactic acid in foods. The importance of lactic acid in the world of food production is well known at present. At the same time, food technologists need accurate, fast, and reliable analytical methods for the determination of naturally present and/or added lactic acid (and related derivatives) in food products and in raw materials. The same thing can be affirmed when speaking of lactic acid as a normal food additive. Naturally, regulatory requirements represent an important demand for adequate and reliable analytical procedures. As a result, the ‘milk acid’ should be detected in foods in a reliable way, on condition that the food matrix and the desired function of lactic acid are well considered. For these reasons, this chapter discusses the practical advantages of several analytical procedures, including spectrophotometry, gas chromatography, capillary electrophoresis, and high-performance liquid chromatography, in relation to selected food categories.

Lactic acid bacteria are widely spread throughout the environment, being symbiotic to humans and among the most important microorganisms used in food fermentations. Despite being a heterogeneous group, lactic acid bacteria share common fermentative pathways, which lead primarily to the production of lactic acid. Their presence in food may be both beneficial and harmful, as their metabolic pathways may also lead to spoilage of certain foods. Furthermore, these microorganisms have gained particular attention due to production of substances of protein structure characterised by an antimicrobial activity (i.e. bacteriocins). These substances are being currently studied for their high potential in the application in food industry for biopreservation, being ‘Generally Recognised As Safe’. Therefore, the role of lactic acid bacteria in the food industry is evolving and promising an always increasing number of applications.