Workshop 8 Flashcards
LIQUID MILKS
Ultra-high pasteurized (UHT) Lactose-free Evaporated Sweetened condensed Soy, rice, almond, cashew, oat
Ultra-high pasteurized (UHT)
Processing at very high temperatures, in aseptic containers, no bacteria, refrigerated
Lactose-free
For lactase deficient people, treated with lactase (converts lactose into glucose & galactose), slightly sweeter
Evaporated
Whole milk with 50% water removed, caramel taste and color due to Maillard reaction (because exposure to high temp), stabilizers and preservatives added for viscosity, collapses easily
Sweetened condensed
Whole milk with sugar, 60% water removed, in dessert & sweets
Soy, rice, almond, cashew, oat
For lactose intolerant or vegan
FERMENTED and PRO-BIOTIC PRODUCTS
Buttermilk Acidophilus milk Sour cream Yogurt Yogurt cheese or labneh Kefir
Buttermilk
Traditionally: by-product of butter-making, separated from cream
Today: add bacterial culture to low or non-fat milk transforms lactose into lactic acid (sour)
Replaced by : milk (250 mL) + vinegar (15mL), lemon juice (15mL) or cream tartar (1 ¾ tsp)
Acidophilus milk
Fermented milk with Lactobacillus acidophilus (naturally in digestive system). Consumed to replenish intestinal flora
Sour cream
From pasteurized milk soured with Streptococcus lactis which produces lactic acid
Homemade: 30mL buttermilk, 500mL fresh cream at room temp for 24hours
Substitute: yogurt (thickened with powdered milk)
Yogurt
Milk product with lactic bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus) Refrigeration slows fermentation.
Gelatin, pectin, carrageen can be added as stabilizers or solidifiers, so whey is less likely to separate from commercial yogurt
Yogurt cheese or labneh
Low fat, creamy cheese
Homemade: suspend within cheesecloth allowing liquid to drain overnight in fridge
If yogurt has gelatin: won’t work
Kefir
Similar to yogurt but fermented with yeast
Fizzy, frothy, piquant, bitter drink
When fermented milk products are subjected to
o Pasteurization or
o UHT
What happens to the bacterial culture?
The bacterial culture is no longer active and their benefits to the digestive system are eliminated
ENERGY AND PROTEIN-DENSE MILK PRODUCTS
High protein milk
Powdered instant or non-instant non-fat dehydrated milk (NFDM)
Whey protein powder
High protein milk
Skim milk powder addition increase protein (1:4 powder:milk)
Full-cream milk: more energy than low-fat
Oil + low fat milk = reduced sat fat content
Powdered instant or non-instant non-fat dehydrated milk (NFDM)
With skim milk : lower fat, less oxidation, less perishable
Used to increase nutritional value of foods though augmentation of protein & energy
Whey protein powder
Made from milk, increases protein intake and energy. Complete high-quality milk whey proteins
How does heat affect whey proteins?
Lactoglobulin & lactalbumin are denatured by heat, coagulate at 66°C (need to stir milk constantly or use double boiler because whey proteins & calcium phosphate precipitate along sides and bottom of the pan and scorch)
How does heat affect casein (milk protein)?
Unaffected by cooking except
o High protein concentration (ex: evaporated, sweetened condensed milk) -> casein curdles
o Boiling an unopened can of condensed milk -> casein will coagulate
How does heat affect sour cream?
sensitive to heat, separates, add just before serving
pH of milk
Milk pH: 6.5-6.7
What happens when pH of milk is below 5.2?
casein begins to coagulate
(because negative charges that stabilize calcium phosphocaseinate micelles are neutralized by hydrogen ions from acid => forms casein salts, milk curdles (high moisture)-> soft & fragile curds formed by acid)
Cheeses made by acid precipitation : high/low in calcium (ex: __ – lactic acid inside)
low
ex: cottage cheese
Used for cheese making, engineered by genetically modified mold Aspergillus
Rennin (sold as rennet)
Optimal activity of rennin
Optimal activity at 40°C and pH 6.7
Steps for curdling of milk when adding rennin
Step 1: rennin cleaves a bond in kappa-casein to from para-kappa-casein to expose chemical groups
Step 2 : exposed groups in para-kappa-casein react with calcium to form a curd because kappa-casein no longer present to stabilize the colloidal dispersion of casein micelles
If milked warmed over 65°C and cooled, what happens?
it won’t clot because of interaction between kappa-casein and beta-lactoglobulin
Which 2 enzymes are used for manufacture of cheese?
Rennin & pepsin
Minimize curdling by
Adding acid to milk (rather than milk to acid)
Heating both acid food and milk before combination
Thickening either the acid food or milk before combination
Serving the combination promptly
Milk foams=
= air bubbles surrounded by thin layers with fat acting as stabilizers
increasing the__ of milk or cream will decrease the tendency of the foam to collapse
viscosity
Increasing__ increases formation & stability of milk foams
fat
Effect of increasing fat on egg white foam
Less stable foam
__ temp causes the fat droplets to harden and clump more easily
COOL
__ delays curdling, prevents over beating, should be added at the end of whipping period
SUGAR
Cheese is high in
Protein, calcium, riboflavin, vitamin A, sodium
2 classes of cheese:
Unripened & Ripened
Unripened
High moisture content Eaten fresh -within few weeks Soft, fragile curd Coagulated primarily by acid Easily homemade Cottage cheese, ricotta
Ripened
Low moisture content
Ripened for 3 months - 2 years
Tough curd, rubbery because of enzyme
Coagulated by enzyme (ex: rennin)
What happens during ripening?
During ripening: casein curd hydrolyzed to amino acids and ammonia, the fat to FA and acetate, the lactose to lactic acid => this breakdown causes cheese to be crumbly
Overheating cheese:
protein coagulates, become tough and rubbery, fat emulsion may break => fat separates
o Egg whites coagulate at __
o Egg yolks coagulate at __
62-65°C
65-70°C
Dilution of egg proteins with __ raises the temperature at which they coagulate
water
What happens when adding acid to egg?
adding acid to egg white (alkaline) decreases the pH to the isoelectric point (least stable) of egg proteins => sensitive to denaturation/ coagulation
What happens when adding salt to eggs?
Salt: lowers the coagulation temperature
What happens when adding sugar to eggs?
elevates the coagulation temperature & produces more tender mixture
FREEZING EGGS
Can only freeze uncooked eggs OUT of their shells in a sealed container for 4 months
Cooked eggs do not freeze well they become rubbery and hard
Yogurt starter=
L. bulgaricus, S. thermophilus, L. acidophilus (5g for 1L)
Used pasteurized egg yolk to limit risk of _
Salmonella
