Patrick F. Fox

Cheese : chemistry, physics, and microbiology

Volume 1: Cheese: An Overview. General and Molecular Aspects of Rennets. The Enzymatic Coagulation of Milk. Secondary (Non-Enzymatic) Phase of Rennet Coagulation and Post. Coagulation Phenomena. The Syneresis of Curd Cheese Starter Cultures. Salt in Cheese: Physical, Chemical and Biological Aspects. Cheese Rheology. Cheese: Methods of Chemical Analysis. Biochemistry of Cheese Ripening. Water Activity in Cheese in Relation to Composition, Stability and Safety. Growth and Survival of Undesirable Bacteria in Cheese. Application of Membrane Separation. Technology for Cheese Production. Acceleration of Cheese Ripening. Nutritional Aspects of Cheese. Index. Volume 2: Cheddar Cheese And Related Dry Salted Cheese Varieties. Dutch-Type Varieties. Swiss-Type Varieties. Mold-Ripened Cheeses. Bacterial Surface Ripened Cheeses. Iberian Cheeses. Italian Cheeses. Ripened Cheese Varieties Native to the Balkan Countries. Cheese of the Former USSR. Domiati and Feta Type Cheeses. Mozzarella and Pizza Cheese. Fresh Acid Curd Cheese Varieties. Some Non-European Cheese Varieties. Processed Cheese Products from Ewes and Goats Milk. Index.

Advanced dairy chemistry

Advanced dairy chemistry , Advanced dairy chemistry , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Proteolysis in cheese during ripening

This chapter discusses proteolysis process in cheese during ripening. Proteolysis contributes to: (1) The development of cheese texture: via hydrolysis of the protein matrix of cheese; via a decrease in aw through changes to water binding by the new carboxylic acid and amino groups liberated on hydrolysis of peptide bonds. These groups are ionized at the pH of cheese and thus bind water; indirectly via an increase in pH caused by the liberation of ammonia from amino acids produced by proteolysis. (2) Flavor and perhaps the off-flavor of cheese, directly by the production of short peptides and amino acids, some of which have flavors; indirectly by the liberation of amino acids, which act as substrates for a range of catabolic reactions, which generate important volatile flavor compounds; by facilitating the release of sapid compounds from the cheese matrix during mastication. Proteolysis in cheese during ripening is catalyzed by proteinases and peptidases from six sources: (1) the coagulant—the enzymes involved depend on the type of coagulant used. (2) the milk—a number of indigenous proteinases are present in milk, the most important of which is plasmin, which is produced from an inactive precursor, plasminogen. (3) starter lactic acid bacteria (LAB) contain a cell envelope-associated proteinase, which contributes to ripening principally by hydrolyzing intermediate-sized and short peptides produced from the caseins by the action of chymosin or plasmin. The other three sources are nonstarter lactic acid bacteria (NSEAB), secondary starter ( Propionibacterium freudenreichii subsp, shermanii in Swiss-type cheese), and exogenous proteinases and peptidases.

Contribution of the indigenous microflora to the maturation of cheddar cheese

Abstract Cheddar cheeses were made from raw milk, pasteurised milk (72°C, 15 s) or milk produced from skim milk which had been microfiltered using an Alfa-Laval MFS-1 MF unit and mixed with pasteurised cream (72°C, 30 s). Microfiltration (MF) reduced the total bacterial count (TBC) by > 99% and MF cheesemilk had a lower TBC than pasteurised milk; counts of non-starter lactic acid bacteria (NSLAB) were

Salt in Cheese: Physical, Chemical and Biological Aspects

The use of salt (NaCl) as a food preservative dates from pre-historic times and, together with fermentation and dehydration (air/sun), is one of the classical methods of food preservation. So useful and widespread was the use of salt as a food preservative in Classical and Medieval times that it was a major item of trade and was used as a form of currency in exchange for goods and labour. It is perhaps a little surprising that Man discovered the application of salt in food preservation so early in civilization since, in contrast to fermentation and dehydration, salting is not a ‘natural event’ in foods but requires a conscious act. It is interesting that the three classical methods of food preservation, i.e. fermentation, dehydration and salting, are all exploited in cheese manufacture and in fact are interdependent. The fourth common method of food preservation, i.e. use of high and/or low temperatures, was less widespread than the others because the exploitation of low temperatures was confined to relatively few areas until the development of mechanical refrigeration about 1870 and, although heating was probably used to extend the shelf-life of foods throughout civilization, its controlled use dates from the work of Nicolas Appert (1794) and Louis Pasteur (c.1840). In modern cheese technology, temperature control complements the other three methods of food preservation.

Cheese: An Overview

Cheese is the most diverse group of dairy products and is, arguably, the most academically interesting and challenging. While most dairy products, if properly manufactured and stored, are biologically, biochemically, chemically, and physically very stable, cheeses are biologically and biochemically dynamic, and are inherently unstable. Throughout manufacture and ripening, cheese production represents a finely orchestrated series of consecutive and concomitant biochemical events, which, if synchronized and balanced, lead to products with highly desirable aromas and flavors but when unbalanced, result in off-flavors and odors.

Heat-induced changes in milk.

In modern dairy technology, milk is almost always subjected to a heat treatment; typical examples are: thermization (65 ˚C × 15 sec), low temperature – long time pasteurization (65 ˚C × 30 min), high temperature – short time (72 ˚C × 15 sec) pasteurization, ultra-high temperature sterilization (140 ˚C × 5 sec), in-container sterilization (112 ˚C × 15 min). The objectives of heat treatment, include: killing heat-sensitive spoilage bacteria (therminization), killing pathogenic bacteria (pasteurization), killing all bacteria, including spores (sterilization), inactivation of enzymes and increasing heat stability. Milk is a very heat – stable system but some chemical and physico-chemical changes do occur in milk on heating. These changes include: damage to the creaming properties, non-enzymatic (Maillard) browning, degradation of lactose to lactulose and acids, denaturation of whey proteins and after severe heat treatment, dephosphorylation and hydrolysis of the caseins and eventually heat-induced coagulation. The principal heat-induced changes in milk are described in this chapter.

Significance and applications of phenolic compounds in the production and quality of milk and dairy products: a review

Abstract A broad range of phenolic compounds (PCs) occur in food products, especially those of plant material, in which they contribute to the organoleptic properties, i.e., astringency, beer hazes, specific (dis)coloration and off-flavours. The occurrence of PCs in milk and dairy products may be a consequence of several factors, e.g., the consumption of particular fodder crops by cattle, the catabolism of proteins by bacteria, contamination with sanitising agents, process-induced incorporation or their deliberate addition as specific flavouring or functional ingredients. The consumption of PC-rich foods by cattle can affect ruminant health and the yield and quality of milk. Indigenous PCs in milk are not thought to pose a health risk to humans and may in fact have some salutary effects. The specific PC profile of milks from different ruminant species appear to play a significant role in the distinct sensory traits of these milks and the products therefrom. At low levels, PCs positively contribute to the desirable taste of cheeses but at high levels are responsible for distinct off-flavours and enzyme-catalysed discoloration. The ability of some PCs to enhance some functional properties of milk and dairy products has also been established, i.e., microbiological stability, foamibility, oxidative stability and heat stability.

Use of the Cd-ninhydrin reagent to assess proteolysis in cheese during ripening

A new method for monitoring the terminal stages of proteolysis in cheese, i.e. the formation of free amino acids, using the Cd-ninhydrin reagent is reported. The assay was very specific for free amino acids and may be performed on citrate-soluble, water-soluble or phosphotungstic acid-soluble fractions of cheese, but not on trichloroacetic acid-soluble extracts; water-soluble extracts were chosen for routine analysis. Application of the assay to several experimental cheeses showed almost linear increases in free amino acids during ripening for up to 12 months with a slightly faster rate of formation during the later stages of ripening.

Autolysis and proteolysis in different strains of starter bacteria during Cheddar cheese ripening

Autolysis of and proteolysis by various Lactococcus lactis subsp. cremoris strains were monitored in cheese ‘juice’ extracted by hydraulic pressure up to 63 d ripening. Viability was lowest for strain AM2 (non-bitter), intermediate for strain HP (bitter) and highest for the defined mixed strains G11/C25 (non-bitter). Autolysis monitored by the levels of the intracellular marker enzymes lactate dehydrogenase (EC 1.1.1.27), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and post-proline dipeptidyl aminopeptidase proceeded in the order AM2 > G11/C25 > HP. Differences in autolysis between strains did not appear to be due to differences in stabilities of the marker enzymes, populations of non-starter lactic acid bacteria or levels of the marker enzymes in the strains. Proteolysis, as measured by gel permeation FPLC and free amino acid analysis of the cheese juice was highest for AM2, intermediate for G11/C25 and lowest for HP. The results of this study provided some evidence that different Lactococcus strains used for cheesemaking had different autolytic patterns during ripening, the effects of which on ripening and flavour development have not yet been clearly demonstrated.