Invited review: Starter lactic acid bacteria survival in cheese: New perspectives on cheese microbiology

Abstract

The importance of starter cultures to cheese manufacture and ripening is well known. Starters are inoculated into cheese milk at a level of ~10 6 cfu/mL either from a bulk culture or using commercial direct-to-vat cultures. Before ripening, starters grow in the milk to reach populations of 10 7 to 10 9 cfu/g of curd depending on processing variables such as cook temperature, inclusion of washing steps, degree of partitioning with curds and whey, and importantly salt addition rate. Inherent strain-related properties also determine final populations in the curd following manufacture and include temperature sensitivity, salt sensitivity, presence of prophage, autolytic and permeabilization properties (which are influenced by processing steps), presence and type of cell envelope proteinase, and metabolic activity. Ripening of important industrial cheese varieties such as Cheddar, Dutch, Swiss, and Italian-type cheese varieties is characterized by extended storage under temperature-controlled conditions enabling characteristic flavor and texture development to occur. Over ripening, microbiological, biochemical and enzymatic changes occur with a decline in starter viability, release of intracellular enzymes, hydrolysis of proteins, carbohydrates and lipids, and formation of a range of volatile and nonvolatile flavor components. Recent reports suggest that starter strains may be present during the later stages of ripening and therefore their potential role needs to be reconsidered. This review will focus on our current understanding of starter viability and vitality during cheese ripening and will also review the area of starter permeabilization, autolysis, and enzyme release.

Omics Approaches to Assess Flavor Development in Cheese

“…The back-slopping technique has been traditionally used for the production of artisanal cheese products, requiring the inoculation of milk with natural milk or whey cultures consisting of unknown strains, termed as undefined starters [55]. Nowadays, starters consist of a specific cocktail of well-defined strains [55], as their survival and spatial distribution within the cheese matrix are strain-dependent properties and can determine the final populations in the curd [56]. [58,59].…”

Microbial communities and volatile profile of Queijo de Azeitão PDO cheese, a traditional Mediterranean thistle-curdled cheese from Portugal

“…In the early cheese-making process, organic acids produced by lactic acid bacteria from the catabolism of carbohydrates (mainly lactose) contribute to milk coagulation. During cheese ripening, lactic acid bacteria release intracellular enzymes responsible for the hydrolysis of proteins and lipids, thus leading to the production of volatile and nonvolatile flavor compounds (Wilkinson & LaPointe, 2020).…”

Lifetime Impact of Cow’s Milk on Overactivation of mTORC1: From Fetal to Childhood Overgrowth, Acne, Diabetes, Cancers, and Neurodegeneration

“…However, an unnoticed dramatic change occurred with the introduction of pasteurization and refrigeration of milk, which preserved milk's bioactive exosomal miRs [132][133][134][135], allowing them to enter the human food chain in large-scale [170,171]. Pasteurization thus preserves milk's bioactive mTORC1 activators including galactose, essential amino acids, and exosomal miRs [132,135,145,160,198,527], whereas fermentation degrades galactose [536][537][538][539], essential branched-chain amino acids [540,541], MEX and their miRs, respectively [393]. Whereas addition of milk to a meal increases postprandial insulin levels [542], addition of yogurt reduces postprandial insulinemia [53], thus reduces insulin-mediated mTORC1 signaling.…”