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ANSC2053 exam 3
milk basics, milk processing, fluid & cultured milk products
| 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 |
Created by:
junoreg
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