The Chemistry Underlying the Differences between Cheese ... · 12/31/2014 7 Please submit questions...

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The Chemistry of Cheese and Why We Love It



Michael Tunick,

USDA

ACS WEBINARS™ May 26, 2011

Bill Courtney,

Cheese-ology Macaroni & Cheese


Michael H. Tunick Dairy & Functional Foods Research Unit

Wyndmoor, PA

Agricultural

Research

Service



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Division of Agricultural and Food Chemistry

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Cheese Chemistry

Americans consume 14 kg of cheese per capita without realizing the extent to which chemistry

is responsible for the production of this food

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Topics

Sources of milk

Cheesemaking

Breakdown of milk components

Flavor compounds and cheese varieties

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Cheese Chemistry

Species and diet of animal producing the milk Processing conditions Storage conditions

Affect structural development and breakdown of Protein Carbohydrates Lipids

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Bovine Milking Breeds

Holsteins represent 90% of US dairy herd

Produce more milk than other breeds

Jerseys make up 7%

Produce more fat and protein

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Ayrshire 7117 kg Guernsey 7318 kg Milking Shorthorn 7286 kg 3.9% f/3.2% p 4.6% f/3.3% p 4.0% f/3.1% p

Holstein 10900 kg milk/yr Jersey 7636 kg Brown Swiss 8528 kg 3.7% fat/3.0% protein 4.8% f/3.6% p 4.1% f/3.4% p

Wendorff and Paulus, Dairy Pipeline 23(1), 1-7 (2011)

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Pasture Compounds

Animals fed on pasture plants have additional compounds in their milk

Terpenes include linalool (floral), α-pinene (pine)

Unsaturated fatty acids break down to form 2,4-decadienal (mayonnaise, bread), nonanal (green), others

Carotenoids lead to citronellol and geranyl acetate (rose), others

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Other Species Provide Milk

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Milk from Goats and Sheep

Contains more short-chain fatty acids, resulting in smaller, more volatile odorant molecules Jensen et al., J. Dairy Sci. 74, 3228-3243 (1991) Park et al., Small Ruminant Res. 68, 88-113 (2007)

Fatty acid Cow Goat Sheep

Butyric, 4:0 3.8 2.2 3.5

Caproic, 6:0 2.4 2.4 2.9

Caprylic, 8:0 1.4 2.7 2.6

Capric, 10:0 3.5 10.0 7.8

Lauric, 12:0 4.6 5.0 4.4

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Cheesemaking

Pasteurize and Standardize Milk

Add Starter Bacteria

Add Rennet

Cut and Cook Curd

Drain Whey

Pile Curds

Mill or Stretch Curds

Add Salt

Press

Coat or Package

Ripen

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Compound and Texture Formation

Enzymes from starter culture microorganisms and coagulant degrade Protein (primarily casein) Carbohydrates (lactose and citrate) Lipids Resulting in Flavor compounds Texture formation

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Starter Culture

Types of starter and coagulant responsible for development of different flavors Usually a combination of Streptococci and Lactobacilli species Lactose lactic acid pH reduced Citric acid metabolized Some proteolysis

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Nonstarter Lactic Acid Bacteria

Starter bacteria decline from 109 to 107 cfu/mL within first month

Adventitious NSLAB proliferate during ripening

From airborne microflora, resistance to heat and disinfection

Include Lactobacillus casei, Lb. plantarum, Lb. curvatus, many others

Contribute to flavor through proteolysis, lipolysis

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Coagulant

Usually rennet, which includes chymosin, pepsin, and lipase

Formerly from calf stomach, now from microbial sources such as Rhizomucor miehei and Cryphonectria parasitica

Chymosin cleaves κ-casein at Phe105-Met106

Casein micelle falls apart

Casein coagulates, forming curds

αs1- and β-casein hydrolyzed

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Proteolysis

plasmin + coagulant

casein peptides

microbial enzymes + coagulant

decarboxylation degradation

amines amino acids sulfur compounds

deamination oxidative deamination

aldehydes α-ketoacids + ammonia carboxylic acids + alcohols methyl thioesters

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Cheese

Microstructure

Cow

Goat Mozzarella

Cheddar

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Cheddar Microstructure During Aging

12 wk

24 wk 36 wk

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Carbohydrate Catabolism

Citrate

Pyruvate 2,3-Butanedione (diacetyl),

2,3-Butanediol,

3-Hydroxy-2-butanone (acetoin)

O-

Ethanal Ethanol

Ethanoic acid

Lactose

Glucose

Galactose

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Lipolysis

triglyceride

lipase

fatty acids

β- 4- or 5- unsaturated free

ketoacids hydroxyacids fatty acids fatty acids

methyl ketones γ- or δ-lactones aldehydes esters

2º alcohols acids + alcohols

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Average Composition

Cheese Type Water Protein Fat Vitamins & Minerals

g/kg

Soft 520 200 220 60

Semi-hard 400 250 270 80

Hard 350 270 310 70*

Very hard 300 290 330 80

*50 g hard cheese contains 40% of RDA of Ca, 15% of vitamin A, 10% of vitamin B2, 20% of vitamin B6, and 40% of vitamin B12

Walther et al., Dairy Sci. Technol. 88, 389-405 (2008)

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Classes of Flavor Compounds

• Alcohols

• Aldehydes

• Amino acids

• Esters

• Fatty acids

• Ketones

• Lactones

• Other compounds

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Most Common Compounds Compound Cheddar Emmental Camembert

Butyric acid 1 1

Propionic acid 4 1

Isovaleric acid 6 2

Ethyl butyrate 2 7

Ethyl caproate 5

Diacetyl 13 5 5

3-Methyl butanal 3 6 3

Methional 8 2 4

Furaneol/ homofuraneol

14 3, 4

Yvon and Rijnen, Int. Dairy J. 11, 185-201 (2001)

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Phenylalanine

Degradation leads to phenylacetaldehyde, phenethylacetate, phenylacetic acid, 2-phenylethanol, phenylethanal

Responsible for floral rose-like notes of Camembert

Responsible for unclean off-flavors in Cheddar

Phenylacetaldehyde responsible for honey-like notes in Gruyère

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Categories of Ripened Cheese

• Very hard (Parmesan, Romano)

• Hard (Cheddar, Colby)

• With eyes (Emmental, Gruyère)

• Pasta filata (Mozzarella, Provolone)

• Interior mold (Roquefort, Stilton)

• Surface mold (Brie, Camembert)

• Smear ripened (Limburger, Brick)

• Brined (Feta, Domiati)

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Cheddar and Colby

Starter: Streptococcus thermophilus and Lactobacillus bulgaricus

Cooking: 38-39°C

Whey removal: Cheddar stacked, Colby washed

Storage: 2-10°C for 2-12 mo

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Cheddar Compounds at 9 Months

Fatty acids (670-3200 mg/kg):

Acetic (vinegar), butyric (cheesy), caproic (sweaty), caprylic (burnt waxy)

Diacetyl (740 μg/kg, buttery)

Methional (200 μg/kg, boiled potato)

Dimethyl trisulfide (7 μg/kg, garlic)

Drake et al., J. Dairy Sci. 93, 5069-5081 (2010)

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Lactones

From lipolysis

Peach/Coconut Flavors

γ-Octalactone δ-Decalactone δ-Dodecalactone

8 μg/kg 34 μg/kg 3 μg/kg

Drake et al., J. Dairy Sci. 93, 5069-5081 (2010)

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Parmesan

Starter: Previous day’s whey

Cooking: Up to 55°C

Storage: 2-10°C for 14 mo to 4 yr

Mostly ethyl esters from C2 to C16

Methyl, propyl, and butyl esters also found

Free amino acids

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Amino Acids

• Bitter Arginine, isoleucine, leucine, methionine, phenylalanine,

tryptophan, tyrosine, valine

• Sweet and bitter Lysine, proline

• Sweet Alanine, glycine, serine, threonine

• Sour Aspartic acid, histidine

• Umami Glutamate McSweeney and Sousa, Lait 80, 293-324 (2000)

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Cheeses with Eyes

Swiss/Emmental Gruyère Cooking: Up to 54°C Storage: 20°C for 4-12 mo Propionibacterium freudenreichii added after lactose

fermentation Lactate converted into ethanoate, propanoate, and CO2,

which collects and forms eyes

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Furans

Furaneol Homofuraneol

Caramel flavors in Emmental

Industrial flavoring agents

Found in wine

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Maillard Reactions

C=O from lactose, glucose,

+ or galactose

lysine

many products

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Maillard Reactions

_ CO2

cysteine

2-thiazoline

2-aminoethanethiol

R

Example: 2-acetyl-thiazoline (popcorn)

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Sulfur-Containing Compounds

Methionine

CH3SH Methanethiol

Dimethyldisulfide Dimethyltrisulfide (garlic, sulfury)

Methionine-γ-lyase

Methional (boiled potato)

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Pasta Filata Cheeses

Mozzarella, Provolone

Traditional Mozzarella made from water buffalo milk

Curd stretched instead of pressed

Mozzarella is meltable with mild flavor

Provolone is aged > 4 mo

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Alcohols

1-Octen-3-ol

From linoleic and linolenic acids

Most common alcohol in cheese

Flavor enhanced by 1-octen-3-one

2-Methylbutanol, 3-methylbutanol, 3-methyl-2-buten-1-ol also found in water buffalo Mozzarella

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Cheeses Ripened by Interior Mold

Roquefort Stilton Blue-green Penicillium roqueforti powder added to

milk or curd Skewered during ripening to introduce oxygen Storage: 5-10°C at 90% humidity for 3-6 mo

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Methyl Ketones

P. Roqueforti converts fatty acids to β-ketoacids

Decarboxylation produces methyl ketones with blue cheese odor

2-Pentanone, 2-heptanone, 2-nonanone, and 2-undecanone common in blue cheese varieties

Enzymatic reduction yields secondary alcohols

2-Heptanol (herbaceous) is key odorant of Gorgonzola

Gkatzionis et al., Food Chem. 113, 506-512 (2009) 54

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Cheeses Ripened by Surface Mold

Brie Camembert 0.5-3 kg wheels 250 g disks

Curd ladled and not broken Surface coated with Penicillium camemberti mold Lactic acid removal increases pH to 7 CaPO4 becomes insoluble and migrates to surface, weakening

protein matrix Ripens from outside over 2-4 wk

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Esters

Produced by reaction of free fatty acid and alcohol

Ethyl esters are dominant since ethanol is most common alcohol available

Ethyl butanoate and ethyl hexanoate found in many cheeses and impart fruity flavors

Branched esters include ethyl isobutanoate (unripe fruit) and ethyl-3-methylbutanoate (fresh cheese)

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Camembert

Compound Odor Concentration (μg/kg )

Odor threshold (μg/kg )

Diacetyl

Buttery 90 10

δ-Decalactone 995 400

3-Methylbutanal Malty 120 13

1-Octen-3-ol Mushroom 100 35

Methional

Sulfurous, garlic-like

75 0.2

Methanethiol 265 0.06

Dimethyl sulfide 330 1.2

Kubícková and Grosch, Int. Dairy J. 8, 17-23 (1998)

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Smear-Ripened Cheeses

Limburger Pont-l’Évêque

Brevibacterium linens (reddish bacterium) brushed on surface after it is first colonized by yeasts

Butanoic, 3-methylbutanoic, caproic acids produced

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Fatty Acids

Variety Concentration (mg/kg )

Mozzarella 360

Limburger 4200

Swiss 4300

Camembert 5070

Cheddar 9500

Parmesan 13700

Roquefort 26000

McSweeney, Int. J. Dairy Technol. 57, 127-144 (2004)

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Feta

Milk: Sheep, with up to 30% goat

Cooking: 34-36°C for 45-60 min

Storage: In barrels containing brine (7% NaCl), at 0-4°C for at least 2 mo

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Aldehydes + NH3 + CO2

Many produced from Strecker degradation

Weenen and van der Ven, in “Aroma Active Compounds in Food,” ACS Symposium Series 794, 183-195 (2001)

H2O -2H

Amino acid Strecker aldehyde Odor threshold (ppb)

Flavor

Isoleucine 2-Methylbutanal 2 Cocoa, fruity

Leucine 3-Methylbutanal 3 Fruity, peach, cocoa

Valine 2-Methylproponal 2 Pungent, fruity

Methionine Methional 0.2 Cooked potato

Phenylalanine Phenylacetaldehyde 4 Honey, sweet, flowery

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The characteristics of cheese depend on the chemistry involved in the way it is made and stored, and knowledge of this chemistry leads to the creation of a better product

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Michael Tunick,

USDA Bill Courtney,

Cheese-ology Macaroni & Cheese



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