Cheese Ripening: Enzymes and Typical Flavour Compounds Associated with Milk Fat Degradation

Abstract

Milk fat is one of the major components of cheese, which occurs as globules surrounded by a thin layer membrane called the milk fat globule membrane (MFGM). This membrane acts as a natural barrier isolating the enzymes from their substrate. However, the MFGM is damaged by the physical treatments applied to milk throughout cheese-making (homogenization, pumping, agitation and foaming, among others). In recent years, some attention has been given to the physicochemical state of the fat since it determines the action of enzymes, mainly lipases and esterases on triglycerides (TG). Enzymatic hydrolysis of fat (known as lipolysis) is the main biochemical event that fat undergoes during ripening, releasing free fatty acids (FFAs). The extent of this process is highly variable among different cheese varieties, depending on the type of lipolytic enzymes present in the cheese matrix, originated from milk, coagulants, primary and secondary starters, and adventitious microorganisms.Fatty acids are also involved in a series of catabolic reactions producing numerous compounds belonging to different chemical families such as ketones, alcohols, lactones and aldehydes. In addition, esters are synthesized from fatty acids through biochemical pathways not yet fully elucidated. Many of these compounds have low perception thresholds and they make an important contribution to the overall cheese flavour.This work proposes a review of the different aspects related to the enzymatic and non-enzymatic synthesis of compounds derived from milk fat and their role and importance in cheese flavour. Moreover, some technological strategies employed to enhance and diversify cheese flavour will be discussed.