Cheese acidification

For cheese sample Ultraturrax homogenization (two cycles) with H2O, centrifugation (for skimming), acidification at pH 4.2. 6 (for casein precipitation), centrifugation, filtration For cheese sample extraction with H2O (sonication) for milk centrifugation, acidification (pH 4.6) to precipitate caseins, centrifugation, filtration... 

The self-assembly of caseins may be readily manipulated by processing methods that affect the integrity of native casein micelles and the character of the casein interactions in aqueous media. Examples of such procedures are (Dickinson, 2006) (i) acidification toward the isoelectric point (p/) (pH 4.6-4.8), leading to a neutralization of the net protein charge (ii) enzyme action, as exploited in the production of cheeses and fermented milks (iii) addition of divalent ions, especially, Ca2+ ions (iv) addition of sucrose or ethanol (v) temperature treatment and (vi) high-pressure treatment. 

Typically, five steps, or groups of steps, are involved in the conversion of milk to cheese curd coagulation, acidification, syneresis (expulsion of whey), moulding/shaping and salting. These steps, which partly overlap, enable the cheesemaker to control the composition of cheese, which, in turn, has a major influence on cheese ripening and quality. 

Acid production is a key feature in the manufacture of all cheese varieties -the pH decreases to about 5 ( 0.3, depending on variety) within 5-20h, at a rate depending on the variety (Figure 10.11). Acidification is normally achieved via the bacterial fermentation of lactose to lactic acid, although an acidogen, usually gluconic acid-<5-lactone, alone or in combination with acid, may be used in some cases, e.g. Mozzarella. 

The contribution of these agents, individually or in various combinations, has been assessed in model cheese systems from which one or more of the agents was excluded or eliminated, e.g. by using an acidogen rather than starter for acidification or manufacturing cheese in a sterile environment to eliminate non-starter lactic acid bacteria (NSLAB). Such model systems have given very useful information on the biochemistry of ripening. 

On acidification to pH 4.6, the caseins coagulate, which is the principle used to manufacture of a family of cheeses which represent about 25% of total cheese consumption and are the principal cheeses in some countries (Appendix 10B). Acidification is traditionally and usually achieved by in situ fermentation of lactose by a Lactococcus starter but direct acidification by acid or acidogen (gluconic acid-d-lactone) is also practised. The principal... 

A method for the determination of 15 BAs in different foodstuffs, namely, Swiss cheese, salami, milk, beer, and wine, was developed by Petridis and Steinhart it is based on an automated precolumn derivatization of BAs [after acidification with TCA and solid-phase extraction (SPE) on Amberlite resin] with OPA/ME and separation on a Spherisorb ODS-2 column with gradient elution (ACN-MeOH-phosphate buffer) and fluorescence detection (71). 

Krause et al. (44) extensively studied the derivatization with DBS, proposed by Chang et al. (76), since DBS reacts with both primary and secondary amines and amino acids at room temperature, leading to stable products detectable in the visible region with high sensitivity. In particular they developed a method for the analysis of BAs, together with the AA, in cheese, seasonings, rice wine, and ham. The deproteinized samples (by ultrafiltration or acidification with TCA) were derivatized with an automated precolumn method and analyzed by RP-HPLC-UV. The DBS derivatization was successively applied to study the occurrence of BAs and free AA in raw-milk cheese (detection at 436 nm). They found that the proportions of free AA and BAs relative to the total amount fell into three broad groups that were independent of the type and ripeness of the cheese (77). 

Tyr, Put, Cad, RP-HPLC with precolumn RP as stationary phase. About 1 mg/L Wine, cheese, fish Acidification, borate buffer 41... 

This is formed of the nitrogenous substances (casein, albumin) and fats contained in milk, separated by coagulation (by rennet or by acidification). As a result of special fermentations which occur during the maturation of the cheese, these give rise to soluble albuminoid substances (albumoses, peptones, etc.), amino-adds (phenylaminopropionic add, tyrosine, leucine, etc.), ammoniacal products, fatty adds (lactic, propionic, caproie), etc. Cheese also contains water and mineral salts, including added sodium chloride. 

In the isolation of casein following the acidification, you removed the precipitate by filtering through a cheese cloth and squeezing the cloth. If you did not squeeze out all the liquids, would your yield of casein be different Explain. 

Acidification to the isolectric pH of casein using lactic acid bacteria or food-grade acids/acidogens, at 20 40 C. and resultant slow quiescent aggregation of the sensitized casein micelles e.g., for cream cheese. [A combination of acidification and rennet-hydrolysis (a smaller quantity of rennet than for rennet-curd cheeses, e.g., 5-100 versus 900-1000 chymosin units per 100 L milk) is normally used for low-fat acid-curd cheeses such as Quark and related varieties (Schulz-Collins and Senge, 2004)]... 

Non-quiescent acidification to pH 5.4-5.6 at a high temperature (80-90°C), [e.g., for Paneer, Ricotta, and some forms of Queso Blanco cheese (Farkye, 2004)]. 

Quarne, E.L., Larson, W.A., Olson, N.F. 1968. Recovery of milk solids in direct acidification and traditional procedures of manufacturing Pizza cheese. J. Dairy Sci. 51, 527-530. 

Whey is the liquid obtained by separating the coagulum from milk, cream, and/or skim milk in cheese making. Whey obtained from the process in which a significant amount of lactose is converted to lactic acid or obtained from the curd formed by direct acidification of milk is known as acid-type Whey. Whey obtained from the process in which there is insignificant conversion of lactose to lactic acid is known as sweet-type Whey. The acidity of Whey may be adjusted by the addition of safe and suitable pH-adjusting ingredients. The final product is pasteurized and is available as a liquid or dry product. 

Recently, Lin et al. [184] used EDBM technology for acidification and decreasing the ionic strength of a fresh cheddar cheese whey. In this study, EDBM process was carried out with or without preliminary decrease of whey mineral salts content by conventional electrodialysis to obtain precipitates with high level of lipids (Figure 21.36). After centrifugation of the treated whey, composition of floes and precipitation yields was determined. 

Lin TSF, Angers P, and Bazinet L. Precipitation of cheddar cheese whey lipids by electrochemical acidification. J. Agric. Food Chem. 2005 53 5635-5639. 

Aside from improved yield, the use of UF pre-cheese results in the improvement of product taste and texture compared to cheese produced by conventional methods because of the reduction of lactose content, controlled acidification rate, and increase in the water-holding capacity of the product due to the incorporation of whey, which makes for softer product [25,73,79]. Lucisano et al. [77] noted an enhanced rennet-induced clotting time of UF-concentrated irulk as pH is lowered from its natural pH level. 

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