Food Fermentations: Dairy Products

Practice vocabulary flashcards covering microbial starter cultures, metabolic pathways, dairy fermentation products, cheesemaking classifications, and probiotics from the Food Fermentations: Dairy Products lecture.

Lactic acid bacteria (LAB)

Gram-positive, usually non-motile, non-spore-forming rods and cocci that obtain ATP by fermenting sugars, thrive under anaerobic conditions, and can grow in the presence of oxygen.

Homofermentative LAB

Lactic acid bacteria that ferment glucose into two moles of lactic acid, yielding a net gain of $2\text{ ATP}$ per mole of glucose metabolized.

Heterofermentative LAB

Lactic acid bacteria that ferment $1\text{ mole}$ of glucose into $1\text{ mole}$ of lactic acid, $1\text{ mole}$ of ethanol, and $1\text{ mole}$ of $CO_2$.

Factors contributing to microbial inhibition by LAB

Inhibitory conditions and antimicrobial compounds produced by lactic acid bacteria, consisting of low pH, organic acids, bacteriocins, hydrogen peroxide, ethanol, diacetyl, nutrient depletion, and low redox potential.

Starter cultures

Preparations of pure microbial strains or tailored species combinations introduced into pasteurized milk to initiate and guide a desired fermentation process.

Diacetyl

The characteristic aroma and flavor compound of cultured buttermilk, synthesized by organisms such as Leuconostoc mesenteroides subsp. cremoris and Lactococcus lactis subsp. lactis.

Cultured buttermilk

A fermented milk product produced with mixed cultures of Lactococcus lactis subsp. cremoris or lactis for acid production ($0.7 - 0.9\%$ lactic acid) and Leuconostoc mesenteroides subsp. cremoris or Lactococcus lactis subsp. lactis for flavor enhancement.

Bulgarian buttermilk

A fermented milk product inoculated with a pure culture of Lactobacillus delbrueckii subsp. bulgaricus.

Acetaldehyde

The primary flavor and aroma compound found in yoghurt, synthesized predominantly by Lactobacillus delbrueckii subsp. bulgaricus.

Yoghurt starter culture ratio

A $1:1$ proportion of Streptococcus thermophilus to Lactobacillus delbrueckii subsp. bulgaricus required to avoid a harsh, sour flavor from overproduction of lactic acid.

Kefir grains

A starter culture matrix composed of bacteria and yeasts embedded within proteins, lipids, and sugars, producing acid, alcohol ($0.5 - 1.0\%$), and $CO_2$.

Acidophilus milk

A fermented dairy product prepared by inoculating milk with a pure culture of Lactobacillus acidophilus.

Rennin

An enzyme added alongside starter cultures to coagulate milk casein, facilitating curd formation and the separation of whey.

Whey

The liquid by-product that separates from the coagulated casein curd during cheese manufacturing, often processed into whey powder.

Hard cheese (LAB ripened)

Cheeses such as Edam, Gouda, and Cheddar that undergo internal ripening throughout the curd exclusively by lactic acid bacteria, with surface growth discouraged.

Hard cheese (LAB + Propionibacteria)

Swiss cheeses such as Emmenthal and Gruyere ripened by LAB and Propionibacterium freudenreichii, which contribute to flavor and eye formation.

Semi-hard veined blue cheese

Cheeses such as Roquefort and Gorgonzola ripened by lactic acid bacteria and Penicillium roqueforti.

Soft surface-mould cheese

Cheeses such as Camembert and Brie that are ripened from the outside inward by lactic acid bacteria and surface mould growth.

Unripened cheese

Soft cheeses made of fresh curd coagulated with rennet and LAB without subsequent ripening, such as cottage cheese, cream cheese, and feta.

Penicillium roqueforti ripening conditions

Inoculation of curds with fungal spores incubated at $9 - 12^\circ\text{C}$ under high humidity conditions, as traditionally found in the caves of Roquefort, France.

Oral probiotics

Living micro-organisms which, upon digestion in certain numbers, exert health benefits beyond inherent basic nutrition.

Probiotic physiological criteria

The physiological requirements for probiotic bacteria to reach the intestine alive: resistance to stomach acid and bile, capability of anaerobic growth, and non-toxicity.

Lactobacillus casei shirota (LCS)

A verified probiotic bacterial strain originating from Yakult and utilized in the commercial product of the same name.

Lactobacillus rhamnosus LGG

A widely researched, verified probiotic strain utilized in dairy and supplement products across more than $25$ countries.

Bifidobacterium animalis DN-173 010 (Bifidus Essentis)

A verified probiotic bacterial strain utilized in commercial dairy products manufactured by Danone.