CHEESE RDL 15, October 1925 n and RD 261/33 casein milk fat mineral salts, vitamins, enzymes microbial flora manufacture, ripening degree

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1 CHEESE RDL 15, October 1925 n and RD 261/33 It is the product of the ripening of curdle, obtained by acid o enzymatic coagulation of whole, skim milk or cream, with or without the addition of salt, color pigments, also by using ferments and sufficiently separated from whey. It is mainly constituted by casein and milk fat, but also by mineral salts, vitamins, enzymes; chemical composition is influenced also by: quality of microbial flora, manufacture, ripening degree. Organoleptic characters vary during the ripening reaching an optimal value and than decreasing. 1

2 Italian products are extremely diverse (various climatic, geographical, cultural conditions) Guarantee of origin have been set up in order to protect the quality of some cheeses MANUFACTURE of CHEESE Milk preparation Curd formation Curdle cut Heating (acid or enzymatic coagulation) Fresh cheese Maturing Salting Storage in moulds Curdle extraction Whey Ripened cheese Fresh cheese Ricotta 2 cheese

3 MILK PREPARATION Fat standardization To obtain fatty cheeses, milk with 3,3-3,4% of fat must be used, for obtaining low fat cheese, starting milk must contain a lower amount of fat. Pasteurization at C/35 or 70 C/10 T must be < 75 C so that coagulation is not compromised Natural milk microorganisms are reduced; Product quality is standardized; Addition of other cultures is needed. It is done mainly in industrial processes. It is needed mainly for fresh cheeses; for ripened cheeses it is sufficient to prepare them working with an high standard of hygiene conditions; possible pathogenic microbes are destroyed due to the maturation conditions: acid ph, presence of salt, natural antibiotics, 3 etc.

Characteristic microflora of some types of cheese Lactic and propionic acid bacteria are the most commonly used; they have acidifying and aromatizing activity.

4 Characteristic microflora of some types of cheese Lactic and propionic acid bacteria are the most commonly used; they have acidifying and aromatizing activity. Some of the most commonly used are: Streptococcus thermophilus Lactococcus lactis subsp. lactis Lactococcus lactis subsp. cremoris Lactococcus lactis subsp. diacetylactis 4

5 FACTORS STABILIZING CASEIN MICELLES NEGATIVE charge at the ph of fresh milk and thus REPULSION Presence of K casein on their surface ACID COAGULATION ENZYMATIC COAGULATION 5

6 CURD FORMATION (or coagulation) Acid coagulation It is caused by lactic acid formed by fermentation (natural or induced by lactic bacteria which were added) of lactose or by addition of weak organic acids (e.g.: citric acid). It is used for the production of soft cheeses (e.g. mascarpone). At the coagulation ph (4.6), calcium is solubilized and thus separates from the curd (curd still binds phosphorous). calcium phosphocaseinate ( soluble colloid) lactic acid or other weak acids (added) acid phosphocaseinate (gelatinous curd) + calcium lactate 6

7 Enzymatic coagulation Rennet (obtained from dry fourth stomach of young calves) is added to milk heated at C. Chymosin (or rennin, that is the active enzyme of rennet) breaks casein into a soluble fraction and an insoluble one (paracasein K); the last one is instable when Ca ++ ion are present and it collapses together with the other micelles causing coagulation as calcium caseinate; in this case much of the calcium phosphate remains in the curd. Calcium phosphocaseinate ( soluble colloid) Calcium paraphosphocaseinate (gelatinous curd) rennet Curd is a gel mass that shrinks keeping fat globules and releasing whey. During curd formation (about 30 ) microflora starts to ferment (pre-maturing). + Glycopeptide (soluble) Lactic acid which is being formed influences curd elasticity. 7

8 CURD CUT-HEATING Curd is cut and gently mixed in order to allow water (whey) to be released. Curd mass is broken into smaller pieces depending on the type of cheese that is being produced and whey is drained off. During the «cut», curd can be heated (38-58 C for 15-1h30 ) depending on the type of cheese. During this step water is further left. The process continues till the desired consistance is reached. PRESSING Curd is separated from whey and can be pressed and molded. MATURING Cheese mass is stored in rooms having proper value of humidity (85-95%) and temperature (3-10 C). In this period (few hours to years, depending on the type of cheese) the product continues to lose water and to fermentate producing lactic acid and many other aroma compounds. 8

9 In the production of fresh cheese some new methods (as ultrafiltration) are being applied in order to include whey proteins in the curd. Whey remaining after curd extraction, contains proteins, lipids (till 1%), lactose and minerals. animal feeding ricotta cheese production: heating at C in order to get whey protein coagulation; the obtained gel mass holds some lactose, fat and mineral and is left dripping for 12h in proper containers. SALTING Dry Brine (18-24% aqueous NaCl) for the taste, as aseptic agent, to accelerate the further loss of water 9

10 LACTIC ACID FORMATION AND FERMENTATION It is formed due to lactic bacteria (or ferments). They use sugar to get energy and they transform it into other molecules. Hydrolysis CC HH OO H 2 HO 2 O C 6 H 12 O 6 + C 6 H 12 O 6 lactose glucose galactose HOMOLACTIC FERMENTATION Isomerization C 12 H 22 O 11 + H 2 O 2 C 6 H 12 O 6 4 OH lactose glucose Propionic fermentation (e.g. in Emmetal cheese) H 3 C HO H O lactic acid about 98% glucose + 2% other products HETEROLACTIC FERMENTATION acetic acid, propionic acid, CO 2 (giving the typical holes). O C 12 H 22 O 11 + H 22 O 2 C 6 H 12 O 6 2 OH + 2 CO CH 3 CH 2 OH lactose glucose H 3 C HO H lactic acid about 50% Lactic acid gives elasticity to the curd, facilitates water loss, inhibits putrefactive bacterial flora. The typical crystals in Grana cheese are due to calcium lactate and phosphate.

11 Protein transformation paracasein proteases Small peptides and free amino acids (giving aroma and flavor) MC = (Maturing Coefficient) Soluble N Total N X 100 MC: 50-80% MC: 30-50% MC: 15-30% MC: < 15% soft cheese with strong mold formation (e.g. Gorgonzola) soft cheese with limited molds formation (e.g. Robiola) hard cheese (e.g. Parmesan) fresh cheese 11

12 Lipid transformations Lactic bacteria have a low lipolitic activity producing only short-medium chain free fatty acids (even in trace they greatly influence aroma); microorganism having an higher lipolitic activity (micrococchi, yiests, molds) provoke also methyl ketone formation (giving odor and taste to Gorgonzola); high lipolisis takes place in soft cheese (to 10 % of fatty acids) and in long ripened cheeses. lipids Fatty acids β-ketoacids metylketons Secondary alcohols Antibiotics production γ and δ hydroxyacids γ and δ lactons saturated Free fatty acids unsaturated hydroperoxides aldehydes acids alcohols Natural production of lactic bacteria (e.g. nisin, policyclic peptide); nisin can also be added as additive (E234). 12

13 NUTRITIONAL VALUE of CHEESE Hard cheeses with low lipids and long ripening are the most digestable; cheeses have the highest content of animal proteins, Ca, P, vitamins A and B; it is a «concentrated food»: 100 g correspond to 1 liter of milk, 1.6 liter in case of Parmesan; high energy value ( kcal/100 g); they don t contain C vitamin, Fe nor carbs (very low amount) and thus should be consumed with cereals (bread, noodles) and vegetables; 100 g of parmesan correspond to 200 g of veal meat, 160 g of ham, 300 g of fish (trout). Average value, in 100 g of cheese Kcalories proteins fat calcium phosphorous (1/5 RDI*) * recommended daily intake g (1/3 RDI) g mg (RDI: 800 mg) mg (RDI: 800 mg) Even if it contains precious nutrients, it is a food that must be consumed in the proper amount (high calories and fat!). 13

14 The ideal balance between calcium and phosphorous and the high content of protein make it ideal for the growth, for bones formation, for teeth. In childhood its consumption is always advisable (at least 30/50 g in a day); In aldults is important since Ca is indispensable for the working of all the organism cells. A constant intake of Ca prevents bones fragility in the elderly. Anyhow, particularly in the elderly, cheese consumption must be limited (max 30/50 g in a day) since it contains much fat. In athletics it is very important for its calcium content, fundamental for the proper working of muscles (80/100 g in a day). In pregnacy and breast feeding is also very important (70/80 g in a day) due to the increased Ca need from 800 a 1000 mg in a day. Also an excess of calcium can give problems: accumulation in urine and kidney stone. 14

15 CHEMICAL ANALYSIS Dry matter Ash Fat (quant./qual.) Pigments Total N and soluble N Research of different origin milk (immunochemical assay in whey protein) Exogeneuous substances Additives (e.g. formaldehyde, E240) Furosin (Maillard product) O COOH O H N 4 NH 2 15

WARM-UP. Grab a. Write down anything written in RED. Milk 4/18/2011. Student Learning Objectives. Terms. Student Learning Objectives

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