| Term | Definition |
| what is milk? | · white fluid produced from the mammary glands of female mammals to nourish their offspring
· an infant mammal's first food is colostrum - transfers immunoglobins, antimicrobial peptides, growth factors to young |
| what is the purpose of milk? | · provide nutrition and well-being to mammalian young
· bridge the nutritional gap between the dependent intrauterine environment and independent adult life
· meet physiological requirements of newborn: colostrum -> passive immunity |
| milk throughout human history | · humans: only species that drink other mammals' milks & consume milk as adults
· those around Kenya/Sudan started drinking milk as adults before they could digest it
· milk nutrient and fat rich -> lactase persistence mutations -> animal domestication |
| sources of milk for human consumption | · cattle: most convenient, widespread availability, large production volumes
· goat (poorer areas), sheep, camel (desert areas), buffalo, equine, yak, red deer, musk ox
· buffalo milk much more popular in 2018 than in 1961 |
| why do humans consume non-cattle milks? | · accessibility: some climates are unsuitable for dairy cattle
· diversification of income: helps farmers cope with fluctuation meat/hair/wool prices
· environment: world limit on dairy cattle is being reached
· added value and nutritional benefits |
| daily consumption of a quart of milk will provide: | · about all the fat, calcium, phosphorus, riboflavin (vitB2) humans need
· 1/2 of protein, 1/4 of calories humans need
· 1/3 of vitA, ascorbic acid (vitC), thiamine (vitB1) humans need
· almost all minerals except iron, copper, manganese, magnesium |
| functions of milk in foods | · can be a standalone beverage, but can also be used as a base for other beverages (hot cocoa)
· food products may be derived directly from milk (yogurt)
· many foods rely on milk or milk ingredients: infant formula, pizza, baked products, etc. |
| functions of milk ingredients | · may improve texture and flavor
· proteins: improve protein content, emulsifiers, stabilizers
· carbs: browning of baked goods |
| basic milk composition | · 90% water, 10% solids
· of those solids: 10% nonfat solids, 4% milkfat
· of those nonfat solids: 5% lactose, 4% protein, 1% minerals
· of those proteins: 3% casein, 0.5% whey
· pH 6.6 |
| milk is a... | · ... oil in water emulsion with fat globules dispersed in the serum phase
· ... colloidal suspension of casein micelles, globular proteins, and lipoprotein particles
· ... solution of lactose, soluble proteins, minerals, and water-soluble vitamins |
| terms to describe milk solids | · plasma: milk - fat = skim/nonfat milk
· serum: plasma - casein micelles = whey (complete protein)
· nonfat milk solids (NMS): milk - fat and water = proteins, lactose, minerals, acids, enzymes, vitamins
· total milk solids (TMS): fat + NMS
· milkfat |
| milk composition among mammal species | · protein: red deer/sheep highest, human/equine lowest
· fat: buffalo/sheep/red deer highest, human/equine lowest
· oligosaccharides: goat and human mostly |
| milk composition among cattle species | · holstein: lowest fat and protein
· jersey: highest fat and protein
· new zealand: middle fat and protein
· all have equivalent lactose, minerals, and water |
| carbohydrate component of milk | · primary is lactose: disaccharide of glucose + galactose, 12g/0.5oz per cup
· oligosaccharides influence infant health: reduce pathogens and encourage beneficial bacteria in GI tract, modulate immune function |
| protein component of milk | · 8g of complete protein per cup
· two main proteins: 80% casein, 18% whey |
| protein component of milk: casein | · four types, αs1-casein, αs2-casein, β-casein, κ-casein
· not very water-soluble: α + β very hydrophobic, κ more hydrophilic
· caseins dispersed as casein micelles |
| protein component of milk: whey | · small, compact, globular and helical proteins
· primarily α-lactalbumin and β-lactoglobulin
· can be isolated through ultrafiltration then used as: emulsifier, foaming agent, gelling agent, improve protein profile of grain-based foods (low in lysine) |
| fat component of milk | · major role in flavor/mouthfeel/stability of milk and its products
· lipoproteins: triglycerides surrounded by phospholipid-protein membranes -> fat globules can be dispersed evenly in fluid
· short chain fatty acids crucial for gut health |
| composition of fatty acids in milk | · 66% saturated
· 30% monounsaturated
· 4% polyunsaturated |
| vitamins in milk | · A, D, B2 (riboflavin), tryptophan (vital in formation of niacin/B3)
· riboflavin lost when exposed to light (packaging and storage important)
· low in C and E |
| vitamin fortification of milk | · fortified with vitD since 1930s in the U.S. to reduce incidence of rickets
· vitA and vitD are fat soluble and are re-added after standardization |
| minerals in milk | · primarily calcium: 1 cup has about 300mg
· phosphorus, potassium, magnesium, sodium, chloride, sulfur
· casein and calcium block intake of dietary iron |
| why is milk white? | · fat, colloidally dispersed casein, calcium complexes, riboflavin (B2)
· higher carotene in feed is dissolved into milkfat -> yellower milk |
| what factors enabled the fate of the dairy industry? | · * mechanical refrigeration *
· pasteurization
· aseptic packaging
· sanitization
· rural electrification
· improved transportation and equipment |
| factors of the demand for milk and its products | · price of milk and its products, availability, season, consumer income, population numbers, changes in consumer preferences
· demand throughout the years: >50% consumed on farm where it was produced in 1909 -> 10% in 1960 -> <0.5% today |
| U.S. consumption trends of milk and its products | · per capita consumption of fluid milk: fell from 2000 to 2021
· per capita consumption of cheese: rose from 2000 to 2020
· per capita consumption of yogurt: rose but evened out from 2000 to 2021 |
| main milk products | · fluid milk (38% of U.S. milk production)
· cheeses (41%)
· soft products: ice cream, yogurt, cream products (12%)
· butter
· dry milk products |
| milk processing steps | · transportation
· storage of raw milk
· separation and standardization
· pasteurization
· homogenization
· cooling and refrigeration
· packaging/making of products |
| bulk milk hauling | · key position, hauler requires a special license
· duties: collect sample for quality tests, measure quantity, transfer milk to transport tank, deliver milk to plant
· quality tests: ensure temp (45F/7C), appearance, flavor, odor |
| storing raw milk | · milk tested for antibiotic residues at arrival, quality determined by bacterial count
· processed within 24hrs arrival at plant, 72hrs max
· raw milk usually stored in silo-type tanks equipped to agitate/stir the milk and hold temp below 45F/7C |
| factors limiting raw milk storage time | · biological: growth, metabolism, enzymatic activity of microorganisms
· chemical: oxidative reactions (less important) |
| separation and standardization of milk | · produces milk of different fat concentrations
· separation: removal of fat (as cream) from milk, usually done by centrifugal separation
· standardization: adjustment of fat concentration to a specific value |
| centrifugal separation of milk | · centrifugal force and density gradient
· heavier skim milk -> out and up, lighter fat globules -> in and up
· efficient separators produce skim milk with no more than 0.01% fat |
| standardization of milk | · milk at arrival to the plant ~3.6-4% fat
· milk at least 3.25% fat (whole milk), reduced fat 2%, skim 0-0.1%
· fat removed for uniform and economically competitive product: cream and milk separated, cream mixed back into skim for desired ratio |
| pasteurization of milk | · heating milk below boiling point (~101C) for short time
· two objectives:
1. destroy nearly 100% of pathogenic bacteria/yeasts/molds and 95-99% of nonpathogenic bacteria
2. inactivate many of the enzymes causing off flavors and rancidity (lipases) |
| pasteurization types (1) | · low-temp long-time: 145F/63C for 30min
· high-temp short-time: 161F/72C for 15sec: denatures less proteins (cheese making), higher temp if other solids added (boiling point up) |
| pasteurization types (2) | · higher-temp shorter-time: 190-270F/88-132C for <2sec, higher pressure, measure exposure by rate of flow
· ultrapasteurization: 280F/138C for >2sec, extends shelf life but needs refirgeration |
| pasteurization types (3) | · ultrahigh temp: 280-302F/138-150C for 2sec, sterilization (aseptic packaging), doesn't require refrigeration, lasts for up to a year |
| does pasteurization damage milk's quality in any way? | · very high temps do little damage to milk flavor during short exposure times, but heating and cooling must be accomplished quickly |
| what size are the fat globules in milk? | · range in diameter from 0.1-16µm
· 80-90% are from 2 to 6µm
· 1.5*10^9 fat globules per mL of milk |
| homogenization of milk | · purpose: disrupt fat globules so >98% are 2µm in diameter and milk has no visible separation after 48hrs at 4-7C
· homogenizers: usually piston-type pumps that force milk through 1 or 2 valves
· fat must be in liquid form (>140F/60C) and pasteurized |
| pros and cons of homogenization | · pros: milk has richer flavor due to smaller particles -> more surface area, is more digestible, and modifies proteins for easier coagulation by heat/acid
· cons: milk for susceptible to off flavors especially by sunlight if lipase still present |
| cooling and refrigeration of milk | · industry depends on this, especially for fluid milk
· increases economic efficiency for producer, processor, and consumer
· reduces rate of deterioration of milk quality: lowers rate of chemical/biochemical reactions that are temp dependent |
| fluid beverage milk sales by product type: trends | · whole milk: sales fell until 1990 then evened out
· reduced fat: sales rose until 1990 then evened out
· low-fat and skim: sales rose slightly from 1975-2020
· flavored: sales rose slightly from 1975-2020 |
| 2020 U.S. dairy vs. plant-based consumption survey | · 71% of respondents: exclusively dairy products
· 24%: both dairy and plant-based products
· 5%: exclusively plant-based products |
| product flow from tank trucks to filling machines in fluid milk processing | · tanker truck -> centrifugal pump -> air eliminator and meter -> raw storage silos -> separator -> clarifier and storage -> HTST unit -> balance tank -> homogenizer -> pasteurization and storage -> filling machines |
| types of fresh fluid cow milks | · whole milk: 3.25% fat, 8.25% NFMS, fortification of vitA and vitD optional
· reduced fat (2%) and low fat (1%): 8.25% NFMS, vitA required, vitD optional
· skim: <0.5% fat, 8.25% NFMS, vitA required, vitD optional, more nutrient in fewer Calories |
| making milk products healthy and desirable | · milk is excellent carrier of fruits, flavorings, probiotics, prebiotics, fiber, and functional ingredients (beneficial to health)
· enhance sales of fluid milk and products, deliver nutrient dense foods to the public |
| amounts of fortification of milk | · whole/low fat: 400IU vitD added per quart
· nonfat: 2000IU/qt vitA and vitD
· other common fortifications: B complex (thiamine, riboflavin, niacin), iron, iodine (protect from light) |
| when should milk be fortified? | · preferably after separation, but can be during standardization or before/during pasteurization
· vitA and vitD are fat soluble -> must be added after separation and standardization for adequate levels |
| probiotic bacteria | · cultured milk products deliver these to the population
· spores can survive adverse conditions like pasteurization (ex. GanedenBC30 - probiotic, spore-forming) |
| flavored fluid milk products | · most popular flavor is chocolate
· others: strawberry, honey, cherry, raspberry, pineapple, apple, orange, banana
· cocoa can provide antioxidants from polyphenols, orange oil slows bacterial growth, vitC in citrus prevents oxidized flavor |
| to be considered chocolate milk, milk must be... | · at least 3.25% fat
· 1.5% liquid chocolate or 1% cocoa + 5% sugar
· otherwise: chocolate flavored drink |
| lactose-free milk | · add yeast-derived lactase to hydrolyze lactose into simple sugars, hydrolysis occurs in final package, ultrafiltration removed ~50% of lactose
· milk has same sweetness as standard milk and allows concentration of proteins for standardization |
| organic milk | · demand has grown significantly in past decade
· refers to quality of ingredients fed to cows producing milk
· NOP specifics: animals must graze pasture for 120 days/year with 30% of dry matter from pasture, protect soil/water quality/feed requirements |
| USDA certification of organic milk | · different requirements depending on status of farm
· for established producing herd: 100% organic feedstuffs, FDA approved additives/supplements/minerals/vitamins |
| what does the USDA prohibit from being in organic milk? | · drugs with hormones, plastic pellets in roughage, urea/manure in feed, mammalian/poultry by-products in feed (fats/rendered products) |
| types of milk packaging | · first was the glass bottle, next was the paper carton
· today: plastic coated paper, blow-molded plastic, plastic bags, glass |
| characteristics of a good consumer milk package | · protects quality through shelf life
· can be handled efficiently in production and distribution
· high merchandising and consumer convenience values
· minimizes packaging costs |
| characteristics of shelf-stable cartons | · from outside to inside:
· outer polyethylene coating (liquid barrier), paperboard (stability), middle polyethylene coating, aluminum (light/odor/oxygen protection), inner polyethylene coating (liquid barrier) |
| characteristics of refrigerated cartons | · from outside to inside:
· polyethylene (liquid barrier), paperboard (stability), polyethylene (liquid barrier) |
| filling milk packages | · precise control in distributing quantity of product is vital: overfill can't be afforded, underfill must be within limits
· milk dispensed with automatic fillers that control and adjust quantity of product
· fill measured by weight but sales on volume |
| requirements of the filling process | · clean packaging area, especially for fluid milk
· air in packaging room must be stable
· operators must change into special clean apparel before entering the room |
| canned milk products | · whole milk canned for export: requirements similar to those for regular whole milk, ultrahigh temp pasteurization required
· also sweetened condensed milk and evaporated milk |
| sweetened condensed milk (canned) | · milk evaporated 50% by weight then 15% sugar added
· must contain 28% total milk solids, 8% fat
· does not need sterilization due to sugar content, ideal for desserts |
| evaporated milk (canned) | · milk evaporated 60% by weight
· 7.5% fat, 25.5% NFMS, 34% of protein from NFMS
· fortified with vitD and stabilizers added to prevent separation
· fat free: <0.5% fat, 20% total solids, vitA and vitD |
| dry milk products | · lighter in transport
· dry milk: all moisture removed, whole/reduced fat/fat free, fortifications optional, similar to fat-free milk but vitamin content 20% reduced, 1yr shelf life
· instant milk |
| basics of cultured milk products | · have been consumed for centuries and are believed to benefit human health
· common products: buttermilk, yogurt, acidophilus milk, kefir (from yeast), sour cream, some cheeses
· often need stabilizers so that whey doesn't separate from coagulated mass |
| characteristics of cultures (cultured milk products) | · bacteria, fungi, yeast (rarer)
· may be naturally present (not required to be on label) or added intentionally (must be listed as ingredient) |
| common steps to preparing cultured milk products | 1. starter culture formation
2. treatment of milk
3. inoculation
4. incubation
5. cooling
6. packaging |
| curd formation (cultured milk products) | · bacterial cultures ferment lactose -> lactic acid
· increased acid concentration -> precipitation of casein -> curd
· type of culture -> flavor of final product
· amount and type of acid produced by bacteria -> quality of final product |
| common bacteria (cultured milk products) | · usually either lactic acid-producing or propionic acid-producing
· Lactobacillus bulgaricus
· Streptococcus thermophilus
· Lactococcus lactis, L. cremoris |
| characteristics of yogurt (cultured milk products) | · among the fastest growing dairy products: has roughly doubled in both lb produced from 2000-2010 and $ profit from 2011-2022
· low calories, highly nutritional, probiotics, many flavors
· add non-fat dry milk for more NFMS and thicker texture |
| common bacterial cultures in yogurt (cultured milk products) | · La. bulgaricus and S. thermophilus -> lactic acid, acetic acid, acetaldehyde |
| yogurt production (cultured milk products) | · high heat treatment: 85C for 10-30 min, denatures whey for water holding capacity and amino acids, nutrient and oxygen availability favor culture growth |
| what do bacterial cultures require for incubation? (cultured milk products) | · bacteria requires: 41-45C incubation temps, ratio of 1:1 to 1:3 of La. bulgaricus : S. thermophilus
· incubation can take up to 8hrs: longer time -> smoother gel, final pH varies from 3.8-4.4 |
| cheese making (cultured milk products) | · phase 1: temp-dependent dissociation of proteins from casein micelles
· phase 2: acid induced gellation between pH 5.4-4.9 -> reassociation of casein proteins into colloidal particles
· phase 3: rapid aggreggation of colloidal casein micelles into gel |
