Fermented Foods Test 2
Feta cheese
Low pH with demineralization lipase may be added rancid flavors desired very crumbly texture final pH 4.6-4.8, can add titanium dioxide to the milk
Buttermilk and sour cream cultures - acid and flavor producers
Acid - lactococcus lactis subspecies. lactis and or cremoris Flavor - leuconostoc lactis leuconostoc mesenteroides subspecies dextranicum or cremoris
What 3 ways can you do coagulation
Acidification to the isoelectric point (mostly soft or unripened cheeses like cottage cheese, cream cheese) Enzymatic hydrolysis of kappa-casein, followed by calcium-mediated coagulation (most hard cheeses like cheddar, swiss, parmesan) Acid + Heat (ricotta, whey cheeses)
What happens during cheddaring?
Acidification, syneresis, de-mineralization, gravity.
What do carbs in cheese produce and contribute to
Acids, alcohols, aldehydes, CO2 contributes to flavor
What is the specialized flavor development in yogurt? in buttermilk and sour cream?
Acetaldehyde in yogurt. Diacetyl in others
Cultured buttermilk quality of starter cultures
Rapid/vigorous growth produce the right body good flavor (Acid and diacetyl) no syneresis
Yogurt quality and defects with starter cultures
Rapid/vigorous growth produce the right body good flavor (acid and acetaldehyde) no syneresis or 'wheezing off' no excess acidity (over acidification)
Sour cream quality of starter cultures
Rapid/vigorous growth produce the right body good flavor (acid and diacetyl)
Milk starter for yogurt
Standardize (nonfat, low-fat or whole) nonfat milk solids (>11%). stabilizers and other ingredients.
cheese ripening Reactions affected by
Temperature, cheese composition, microorganism in the cheese
Trends in yogurt technology
Texture-enhanced (whipped, extra thick, custard), greek-style (Strained), fluid (drinks, smoothies), mild-flavored (especially low acid), probiotic/prebiotic, frozen
Issues in the cheese industry
Yield (Cheese as well as fat and protein) Bitterness Whey (Utilization of constituents) Bacteriophage Quality: Flavor, texture, color, crystals, mold, physical appearance
Cheese coagulated by chymosin
rely on kappa-casein on ca2+ mediated precipitation used for most cheese types fermentation is needed for flavor, preservation and function.
fermented cabbage
sauerkraut
Muenster short list
surface growth, with orange-red pigment, brevibacterium linens, sulfury flavors, US (milder) versions have little or no surface growth
What about the yogurt culture
symbiosis, synergism, mutualism, proto=cooperation bottom line- both grow better together than apart. have higher growth rates and cell densities and more end products produced. relevant ing YOGURT AND CHEESE Need ratio of 1:1 because influences final product
What is the isoelectric point?
the pH at which the net charge of a protein is zero. Or at it's isoelectric point a protein is at it's minimum solubility.
What happens upon the hydrolysis of kappa casein
the surface charge of the remaining micelle is dissipated, and the core subunits have greater access to calcium.
Overall goal about cheese manufacture
to control microbial, enzymatic and chemical reactions
What does l bulgaricus do for s thermophilus
Hydrolyzes protein, provides amino acids and peptides.
What does lactic acid break down into for swiss cheese fermentation
3 lactic acid goes to 2 propionic acid, 1 acetic acid and 1 CO2
HT for yogurt
85C for 30 minutes (90C for 15) or 95 for 8-10
4 main fractions of casein chemistry
Alpha s1, alpha s2, beta, kappa
Mozzarella cheese manufacture
Also relies on 'cheddaring' process, fermentation after cooking, then brine-salted pH 5.1-5.2 is critical for proper stretching
What do proteins in cheese produce and contribute to
Amines, peptides, NH3 Contributes to flavor and texture
Principles of isoelectric precipitation
Amino acids can either be neutral or they can carry negative or positive charges. these charges can cause electrostatic repulsion, which helps maintain protein in solution, as charge repulsion is dissipated, protein becomes less soluble and eventually it will precipitate.
Measuring cheese ripening
Analytical techniques, aka electronic noses (GC, GC-MS) Protein electrophoretic techniques (1 or 2-D) Soluble nitrogen, free fatty acid Sensory analysis
How can milk proteins be separated
By enzymatic means or via isoelectric precipitation
Role of calcium in cheese texture
Calcium-casein needed to maintain plasticity, lower the curd calcium, the more crumbly is the cheese, lower the pH, more calcium is lost, therefore, can influence texture by controlling calcium (de-mineralization)
Acid mediated coagulations
IF you add acid, the acid takes way available calcium ions which causes the structure to not bind as tightly
Casein chemistry
Casein refers to group of serveral different proteins. They are negatively charged due to presence of phosphate groups attached to serine residues
cheese ripening involves
Chemical reactions, enzymatic reactions and physical phenomenon -changes occur in flavor, texture, appearance, rheology
Cheese ripening enzymes from
lysed bacteria, milk, coagulant
mozzarella cheese: functional properties
Color (browning), stretch, oiling off, melting, spreadability, flavor
What is cheese ripening
Controlled spoilage
What determines the moisture content
Cooking/stirring
Cheese coagulated by chymosin factors that influence final product
Curd handling, acidification, salt, culture activity, shape and form and cook temperature
parmesan, grana, other hard grating cheeses
Dry, with hard rinds thermophilic cultures nutty, sharp, savory flavors
What is the take home message of EPS
Expression of EPS is complicated and obtaining consistent production can be challenging
What is the purpose of cooking cheddar cheese?
Firm the curds, enhance syneresis, and control culture activity.
Types of stabilizers in yogurt and cultured dairy products
Gelatin, starch (native and modified), pectin, gums (carrageenan, guar, alginate, locust bean), exopolysaccharides (EPS)
Accelerated ripening
Goal: achieve aged cheese flavor in less time Adjust temperature (from 8-10 to 12-18) add adjuncts add enzymes (EMC)
Citrate fermenting cheese culture
Leuconostoc lactis and other leuconostoc sp.
What are cheese types based on?
Hardness, acidification method, moisture content, cooking temperature, mode of ripening, extent of aging, and distinguishing characteristics
Cheese precipitated by acid + Heat methods
Heat can be via direct or indirect (steam infusion) Acidification is via sour whey or milk or food-grade acids Flavor is rather bland to slightly sweet, but usually have excellent functional properties (melting, slicing, mouth-feel, etc.)
Alpha s1 and s2 casein fractions
High negative charge charge, high phosphate content, and calcium-sensitive
Flavor compounds in cheese
Hundreds of compounds, some have very low thresholds (ppm) for flavor, A little may be good, too much is a defect for example, a little h2s in cheddar is desirable, but too much is a defect 2 ppm methyl ketone in cheddar is fine, and 90 ppm in blue is fine, but 90 ppm in cheddar is not so good
What are the main principles of cultured dairy products?
Isoelectric precipitation, no whey removal, minimize syneresis, and specialized flavor development
Yogurt quality and defects with flavor defects
Lack of flavor too much flavor poor flavor yeasty (from fruit) unclean, bitter (from milk)
Sour cream defects of starter cultures
Lacks flavor caused by not enough citrate fermenters, incubation temperature too high or too low, product too fresh (best after 72 h) Too much acid, harsh wheying off too thin (firmness very important) yeasty, unclean
Cultured buttermilk defects of starter cultures
Lacks flavor caused by not enough citrate fermenters, incubation temperature too high or too low, product too fresh (best after 72 h) Too much acid, harsh wheying off too viscous, too thin yeasty, unclean
Mesophilic dairy starter cultures
Lactococcus lactis subspecies lactis (and biovar diacetylactis) and lactococcus acties subsp cremoris
Mesophilic cheese cultures
Lactococcus lactis subspecies. lactis, lactococcus lactis subspecies. cremoris -used for medium cook cheeses
Growth of LAB in milk
Lactose is rapidly fermented, lactic acid is produced. at pH 4.9-5.2, casein becomes 'destabilized' and at 4.6-4.7 precipitation (coagulation) occurs Minimal protein degradation occurs in cultured products, much more important in cheese. other end-products important for flavor and texture.
Citrate-fermenting (for flavor) dairy starter cultures
Leuconostoc lactis Leuconostoc mesenteroides subspecies. cremoris Leuconostoc mesenteroides subspecies. dextranicum
What is annatto?
Natural coloring added to cheeses
Buttermilk and sour cream cultures - characteristics
Need an acid producer and flavor producer, too much or not enough acid inhibits flavor production, control managed by inoculum and incubation temperature, acid producer:flavor producer ratio about 5:1 to 6:1. incubation temperature 20-22C, higher temperatures favor lactococci (acid producer)
Yogurt texture and rheology - weak body
Not enough solids, insufficient heat treatment insufficient stabilizers
Yogurt texture and rheology - syneresis
Not enough solids, insufficient heat treatment, rough handling, high acidity
Kapa casin fraction
Quite different from other casein fractions, glycoprotein substrate for chymosin
Exopolysaccharides produced by LAB
Referred to as 'ropiness,' EPS provide important rheological and functional properties in food. capsular (attached to cell surface) or secreted Produced by thermophilic and mesophilic strains. chromosomal or plasmid-encoded production is not constitutive and is subject to growth phase, substrate availably and other factors Homopolysaccharide or heteropolysaccharide.
Cheddar cheese manufacture
Relies on 'cheddaring' process Fermentation after cooking, then dry-salted pH 5.1-5.2, 2.25% salt, 37-39% H2O, 50% fdb
Cheese precipitated by acid + Heat
Rely on high heat (>80C) and slightly acid (pH 5-6) Denatured whey proteins co-precipitate with casein Can use milk or whey Usually soft, fresh, unripened cheeses like ricotta, queso blanco and paneer.
Acid-precipitated cheese
Rely on isoelectric precipitation of casein most are unripened examples include: cottage cheese, cream cheese Can reach pH 4.6-4.7 one of two ways 1. fermentation and lactic acid formation 2. direct acidification by adding food grade acids (lactic, gluconic acid) (advantages is no culture preparation needed, faster, more convenient, but has lack of flavor, and labeling.
Principle of cheese manufacture
Remove water, concentrate protein and fat, flavor and texture development (via microbial, enzymatic, and physical-chemical reactions), long shelf life
Blue cheese
Requires aeration penicillium roqueforti flavor from lipolysis, fatty acid metabolism and formation of methyl ketones pH 4.5-4.5 after fermentation. pH 6.5 at the end of aging
Swiss cheese "easy to make, but difficult to make well"
Requires just the right texture, pH, and moisture to obtain perfect eye formation Too soft, too dry, too acidic, too sweet, all result in quality defects Therefore, need to control multiple variables to achieve a high quality product
Buttermilk
Rich in phospholipids and other natural emulsifier and is widely used in the food industry. when making cultured buttermilk with a lactic culture, the buttermilk also was fermented, hence the product we have today
Swiss cheese manufacture
Slow (overnight) fermentation, then brine-salted, pH 5.2 is critical, propionibacterium shermanii grow later
How are the composites of milk arranged in milk?
Some dissolved, some colloidal, dispersed, suspended, or emulsified.
What are the yogurt cultures?
Strep. thermophilus and lactobacillus delbrueckii subspecies bulgaricus
Thermophilic cheese cultures
Streptococcus thermophilus lactobacillus helveticus or lactobacillus subspecies. delbrueckii bulgaricus -used for high-cook, dry cheeses more commercially important due to increased popularity of these cheeses
Thermophilic dairy starter cultures
Streptococcus thermophilus: paired with lactobacillus helveticus (in cheese) or lactobacillus delbrueckii subspecies. bulgaricus (in yogurt)
Brie short list
Surface growth, penicillium camemberti, flavor from protein and fat metabolism (NH3) Consumer preferences vary (mind to strong flavor) pH 4.6-4.9 after fermentation, pH 7.0 at end of ripening
How to separate milk proteins
Use chymosin or ph 4.6-5.7 and whey proteins will be in solution (0.8 g protein/100 ml so 20% of total milk protein) and casein will precipitate (2.5 g protein/100 ml so 80% of total milk protein)
Beta casein fractions
Very hydrophobic, proline-rich
General composition of milk
Water - 87-88% Carbs - 4.9-5.0% Lipid - 3.5 - 4.0% Protein - 3.3% (Casein 2.5% and whey proteins 0.8%) mineral (ash) 0.7%
Edam, gouda short list
Whey dilution, pH around 5.4, leuconostoc or other citrate fermentors, buttery flavors, few small eyes are possible
What does s. thermophilus do for L. bulgaricus
acidifies the milk, produces co2 and reduces the eh, produces small amount of formate, other organic acids
Cheese coagulated by chymosin post-manufacturing steps (ripening) also important
adjunct organisms, temperature and humidity, and culture activity
Function of stabilizers in yogurt and cultured dairy products
bind water, reduce syneresis, increase viscosity, improve consistency, maintain gel structure, especially important in stirred products
calcium in whey
calcium lost in whey is lost forever! calcium lost in curd is retained.
Washed curd cheeses
colby, monterey jack, new york cheddar, dutch cheeses, brick/limburger/munster Dilutes out lactose, results in less acid formed during fermentation Hot water performs like cooking (enhances syneresis and decreases moisture content) Cold water has the opposite effect, as water is adsorbed and moisture content increases (although lactose dilution still occurs)
properties of kappa casein
contains carbs (a glycoprotein), peptide consists of 169 amino acids, peptide bond between residue 105 and 106 is sensitive to hydrolysis by chymosin, when hydrolyzed kappa casein is no longer intact and two products are formed. so stabilizing property is lost
2 ways amino acid is metabolized and the end product
deamination (NH3) goes to keto acid Decarboxylation (CO2) goes to amine
Yogurt texture and rheology - too firm or viscous
excessive stabilizers, choice of stabilizers, EPS from the culture
What determines the pH of the cheese?
fermentation of lactose
role of salt
flavor, enhance syneresis, inhibitory to spoilage and other microorganisms (i.e., preservation) Controls growth of desirable microorganisms controls enzyme activity contributes to rind formation the 'percent' salt is not the relevant value, rather the salt-in-moisture (s/M) is more relevant
What do lipids in cheese produce and contribute to
free fatty acids, ketones contributes to flavor
Exerting control during cheese manufacture
how to control acidification (pH) How to control moisture content (aw) how to control texture development how to control flavor development how to control redox potential (Eh) ACTIVITIES ARE INTERRELATED
The casein micelle
large, disorganized, spherically-shaped aggregates that consist of 'sub-micelles' (raspberry like) alpha and beta are located within the core of the micelle and kappa is at the exterior. kappa fraction stabilizes the micelle and blocks the negatively charge phosphate groups inside
What determines how much lactose is available?
moisture in curd
carb utilization and culture growth during swiss cheese fermentation
must be at pH 5.2 +/- 0.1 for proper eye development Too low inhibits P. shermanii Too higher promotes overgrowth of p shermanii FInal ph around 5.6
What do minerals in cheese produce and contribute to
no products, contributes to texture
fermented olives
olives
Mozzarella
pH 5.1-5.2 is critical for proper stretching fermentation is incomplete, residual sugars are important. thermophilic LAB functional properties are critical
ph and aw of milk
pH 6.6 - 6.8 aw - 0.999
What products are formed from the hydrolysis of kappa casein
para-kappa-casein and glycomacropeptide
Fermented cucumbers
pickles
