Milk and Milk Products Questions

Dairy microbiology — alkaline reaction in milk: Which organisms are classic “alkali formers” that cause an alkaline shift in stored raw milk due to protein breakdown and ammonia release?

Butter defects — Pseudomonas nigrifaciens in lightly salted butter: Which characteristic defect does Pseudomonas nigrifaciens cause in mildly salted butter?

Cream layer discoloration — yellow pigment producers: A yellow coloration in the creamy layer of milk is most commonly associated with which organism?

Sweetened condensed milk — principal spoilage type: What is the chief spoilage problem encountered in sweetened condensed milk under improper storage or contamination?

Butter off-flavors — “fishiness” defect: Which organism is classically implicated in producing a fishy off-flavor in butter under poor hygiene or storage conditions?

Milk discoloration — brown color development: Brown color in stored milk can result from which of the following causes?

Therapeutic cultured dairy — acidophilus milk: Manufacture of “acidophilus milk” for intestinal health requires a pure culture of which microorganism?

Butter flavor defects — ester (fruity) notes: Which organism is commonly associated with forming ester-like, fruity flavors in butter during spoilage?

Flavor defects — Streptococcus lactis var. maltigenes: Certain strains of Streptococcus lactis var. maltigenes are known to produce which characteristic off-flavor in milk products?

Canned dairy/foods — can swelling and gas defects: Swelling (bulging) of hermetically sealed cans is caused primarily by which group of microorganisms?

Dairy microbiology — “cheese cancer” defect in Swiss-type cheeses In Swiss and related hard cheeses, the defect historically termed “cheese cancer” (a surface, cratered, casein-digesting growth) is caused by which microorganism?

Cheese discoloration defects — Clostridium species causing dark green to black colours in cheese Which Clostridium species is most associated with the formation of dark green to black discoloration in cheese during ripening or storage?

Milk discoloration — pigment defect produced by Pseudomonas syncyanea What characteristic color change does Pseudomonas syncyanea produce in milk when grown in pure culture under chill conditions?

Cultured milk beverages — starter(s) used for “Bulgarian buttermilk” Which microorganism is classically credited as the primary culture for producing Bulgarian buttermilk in traditional dairy practice?

Butter defects — “surface taint” attributed to Pseudomonas putrefaciens The surface taint in butter caused by Pseudomonas putrefaciens is also commonly referred to as which of the following?

Yogurt manufacture — starter composition used in commercial practice Modern yogurt is produced using which starter culture combination to achieve rapid acidification and characteristic flavor?

Ropiness in milk — vertical distribution pattern with Enterobacter spoilage When ropiness in milk is caused by Enterobacter species, where is the defect typically most pronounced within the container?

Cheese sliminess under low acidity — likely bacterial culprits Cheese made with too low an acidity (for example, due to added cream or weak starter) is often rendered gelatinous or slimy by which organisms?

Non-bacterial ropiness/sliminess in milk — physical and physiological causes Which of the following are recognized non-bacterial reasons for ropiness or sliminess in milk and milk products?

Aromatic acidity in cultured dairy products — microbial combination responsible for aroma development In cultured milks, the acidity may be described as “aromatic” under which microbial growth combination or condition?