Enzymes and Dairy Products: Focus on Functional Products

Introduction

Enzymes are usually proteins that occur in all living organisms with biological catalytic activity, and they are used in several industrial applications, including food processing. As a catalyst, an enzyme works to accelerate biological and biochemical reactions necessary to support life by lowering the activation energy involved in the reaction (Olempska-Beer et al., 2006). These macromolecules appeared for the first time more than 5,000 years ago with the storage of milk in an animal’s stomach that contained enzymes called rennet, which turn milk into cheese (Novozymes, 2017).

Enzymes have several applications in the food industry because of their high specificity, effectiveness in small quantities and catalytic activity under mild temperature and pH conditions. Their high specificity minimizes unwanted byproducts formation, since they catalyze the conversion of only a single substrate or a small group of closely related compounds or a specific bond. Furthermore, because they are active in small amounts, low usage levels make enzymes economical and practical for commercial application. Another advantage is related to their capacity to actuate under mild pH and temperature conditions, which reduce energy costs (James and Simpson, 1996). However, the use of enzymes in the food industry, including dairy products, is still below expected levels, mainly due the high costs involved in their production and purification, which will be further discussed.

Enzymes can be produced by animals, plants and microorganisms, which mean that they originate from natural sources and therefore are desired for food process. Microbial sources have great potential for industrial applications since they can be produced by fermentation on a large scale. Furthermore, they are easily expressed by cloning in well-known cultivated microorganisms (Gandhi, 1997). The use of recombinant DNA technology has also made it possible to manufacture novel enzymes suitable for specific food processing conditions and to increase enzyme production, reducing processing costs. Nevertheless, there are also immobilized enzyme systems which are used to overcome inhibition problems and to lower the costs of enzymes, since the purification step can be omitted.

The application of enzymes in dairy products is well established, where proteases, lipases, esterases, lactase and catalase are the most common enzymes found in these products. According to Afroz et al. (2015), rennet, a mixture of chymosin (or rennin) and pepsin produced by animal and microbial sources, are used for milk coagulation in the first stage of cheese production. Proteases are used to accelerate cheese ripening, to modify functional properties and also to promote the alteration of milk proteins to reduce the allergenic properties of cow’s milk products for babies. Lipases are used for cheese ripening and contribute to the development of lipolytic flavors. Lactase or β-galactosidase (from microorganisms) is used to hydrolyze lactose to glucose and galactose so the product is more digestible by lactose intolerant individuals, and also to improve the solubility and sweetness of dairy products. Peptidases are used to break down bitter peptides that appear in ripened cheese and thus assist in providing the traditional cheese flavor.

It is certain that increased concern regarding energy scarcity and required protection of the environment may lead to deeper knowledge on enzymatic processes, including those for food processing. Therefore, studies on enzymology are currently being conducted to make improvements to dairy products. The aim is to find enzymes with technological advantages that do not noticeably alter the sensory characteristics of the dairy products. Another tendency is to use enzymes with functional properties that permit the production of high added-value dairy products, such as glucose oxidase and bile salt hydrolase (BSH).