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The structure of food plays an important role in determining rate of digestion by influencing the disintegration rate and affecting the release of bioaccessible components. In the stomach, breakdown of food structure occurs through mechanical peristaltic forces and hydrolysis of macronutrients. The objective of this study was to investigate the gastric digestion of Cheddar, Mozzarella, and Parmesan cheeses using both static soaking method and dynamic in vitro gastric digestion model. During static soaking in simulated gastric juice, cheeses had less texture softening at lower pH. Mozzarella cheese showed texture hardening behavior, leading to the lowest rate of nutrient leaching among the three cheeses, while Parmesan cheese had the highest rate of nutrient leaching. During dynamic gastric simulation, Mozzarella cheese showed the most resistance to protein hydrolysis by generating only 6.81 g/L amino acids when compared to 12.70 g/L and 24.3 g/L amino acids released by Cheddar and Parmesan cheese, respectively. The resistance of Mozzarella cheese was attributed to the dense outside layer formed due to aggregation of the protein matrix at highly acidic environment that encapsulated the cheese particles and prevented gastric juice from further digesting the proteins.

The fate of AFM1 during production of a long maturing cheese (Parmesan cheese) was assessed. Different levels of AFM1 contamination and of the fat/casein (F/C) ratio of milk were considered, in order to evaluate if these factors can influence the enrichment factor (EF) of AFM1 in cheese. For this purpose, 24 cheese-makings were carried out using naturally contaminated milk at 3 different AFM1 levels and at 2 F/C ratios. AFM1 analysis was performed by HPLC in raw milk, cream, cauldron milk, liquid cattle rennet, whey, curd and cheese at 3, 9, 16 and 24 months of ageing. The mass balances of the cheese-making processes were close to 100%; in whey, AFM1 concentration was about 40% less than the concentration in cauldron milk. The EF in curd was between 4.0 and 5.2, with an average value of 4.7 ± 0.4; this factor was not significantly affected by either AFM1 contamination level or F/C ratio. During maturation, AFM1 concentration and consequently EF increased from curd to 16 ageing months; successively, AFM1 slightly decreased at 24 months and consequently the EF. At 3, 9, 16 months of maturation, the EF was significantly higher for cheeses prepared using milk with low F/C than those with high F/C milk; on the contrary, EF was not significantly influenced by the AFM1 contamination level. In cheeses, EF values were between 4.7 and 6.3; from these results, the maximum admissible level for AFM1 in Parmesan cheese should be about 0.275 μg kg−1.

Diversity and dynamics of autochthonous microbiota of Cotija, a traditional Mexican raw-milk cheese that resembles Parmesan, were compared in cheeses during 90 days of ripening under traditional and controlled conditions (temperature and relative humidity). Molecular assessments by PCR-DGGE 26S and 16S rRNA encoding regions were performed on various sections of the cheese at different ripening times. A complex microbial profile was found differentially distributed in the cheese. Several spices of lactic-acid-bacteria (LAB) from the genera Leuconostoc, Lactobacillus, Weissella , Aerococcus, Enterococcus, Carnobacterium and the yeasts Candida etchellsii, Pichia kudriavzevii and Moniliella suaveolens were found in the cheese matrix, with Leuconostoc mesenteroides being dominant. The cheese surface was populated by some of these microorganisms before the characteristic crust was formed, but Kluyveromyces lactis, Kodamaea ohmeri together with non-lactic-acid-bacteria (nLAB) Psychrobacter celer and Corynebacter variabile became distinctive in this part of the cheese. The microbial spatial/temporal variations showed similar patterns in samples from both ripening conditions, which suggested a robust ecosystem that is likely responsible for the safety, sensorial richness, and potential bio-functionality of Cotija. This knowledge could open the possibility for standardizing the ripening operation to avoid defects and improve the marketing of the product.

Ion-pair-HPLC, post-column derivatization with o- phthalaldehyde and fluorimetric detection is the method of choice for the separation and quantification of bioactive amines in foods. However, there is still no consensus on which methodology is the most appropriate for the extraction of the amines from different food matrices. The efficiency of chloridric, trichloroacetic, perchloric, sulfosalicylic and acetic acids, borate buffer, methanol and ethanol in the extraction of ten bioactive amines from grated Parmesan cheese was investigated. Extraction efficiency was affected by the levels of amines present in the sample and by the type, concentration and temperature of the extractor, and the method used. When selective extraction of amines from grated cheese was desired, the polyamines—spermine and spermidine—were better recovered by HCl; agmatine was better extracted by borate buffer or HCl; the aliphatic amines—putrescine and cadaverine—were more efficiently extracted by borate buffer and HCl; whereas the aromatic amines—tyramine and phenylethylamine—and the indolamines—tryptamine and serotonin—were better recovered with organic solvents. For the adequate extraction of most of the amines from the grated cheese matrix, 1.0 m HCl was chosen, providing good recoveries for most of the amines. Furthermore it is a relatively simple, inexpensive and rapid procedure.

The state-of-the-art and current trends in the development of “aroma” analysis with electronic noses are reviewed with special reference to applications to dairy-products. Some of the reported problems with electronic noses have recently been reduced, e.g. the correction/reduction of signal drift, the influence of humidity and temperature. New promising and reproducible sensor manufacturing techniques are being implemented, e.g. electro-spray for QMB sensor production. The development of more selective and sensitive sensors, especially of QMB and conducting polymer (CP) type, should improve their applicability. Interesting novel sampling techniques, such as SPME or SBSE, offer more possibilities for the analysis of semi-volatile compounds which are generally more odoriferous. However, standard calibration procedures and reference materials are not yet available. Although they are normally less powerful than human noses, electronic noses offer some significant advantages in the analysis of volatiles, for example, in instrumental classifications based on hedonic or sensory analyses and in potentially automated on-line monitoring of volatiles. Several groups have explored the application of different electronic noses in the investigation of various aspects of dairy products. The present review includes as examples the evaluation of Swiss and Cheddar cheese aroma, the assessment of the ripening of Pecorino Toscano cheese (ewe’s), the detection of mould in Parmesan cheese, the classification of milk by trademark, by fat level and by preservation process, the classification and the quantification of off-flavours in milk, the evaluation of Maillard reactions during heating processes in block-milk, as well as the identification of single strains of disinfectant–resistant bacteria in mixed cultures in milk. © 2003 Elsevier Science B.V. All rights reserved.

The efficacy of three culture media, dichloran rose bengal chloramphenicol (DRBC), dichloran 18% glycerol agar (DG18), and potato dextrose agar (PDA) supplemented with two antibiotics, were compared with the Simplate and Petrifilm techniques for mold and yeast enumeration. The following foods were analyzed: corn meal, wheat flour, cassava flour, bread crumbs, whole meal, sliced bread, ground peanuts, mozzarella cheese, grated parmesan cheese, cheese rolls, orange juice, pineapple pulp, pineapple cake, and mushroom in conserve. Correlation coefficients of DRBC versus PDA and DG18 for recovering total mold and yeast counts from the composite of 14 foods indicated that the three media were generally equivalent. Correlation coefficients for Petrifilm versus culture media were acceptable, although not as good as between culture media. Correlation coefficients of Simplate versus DRBC, DG18, PDA, and Petrifilm for recovering total yeasts and molds from a composite of 11 foods demonstrated that there was no equivalence between the counts obtained by Simplate and other culture media and Petrifilm, with significant differences observed for the most foods analyzed.

Volatile constituents present in the water-soluble fraction (WSF) of eight hard-type cheeses (Cheddar, Edam, Gouda, Gouda 20+, Proosdij, Maasdam, Gruyere and Parmesan) were isolated and identified by using a dynamic headspace technique. The compounds were isolated from the WSF of cheeses by purge-and-trap extraction and analysed by gas chromatography-mass spectrometry. Fifty-three components were identified and 25 were quantitatively determined. The volatiles belonged to six major groups: fatty acids, esters, aldehydes, alcohols, ketones and sulphur compounds. Most of them were present in the WSF of all eight types of cheese studied. The aroma characteristics of the volatiles and their possible formation from compounds like fats, lactose and amino acids, are described.

The starter used in the production of Parmesan cheese consists of mixed-strain whey cultures of thermophilic rod lactic acid bacteria, where several strains of each species can be found. The present work was undertaken to demonstrate the effects on the strain composition of interactions among individual lactobacilli grown together in cheese whey. Three strains belonging to Lactobacillus helveticus and Lactobacillus delbrueckii subsp. bulgaricus and subsp. lactis were cultured in Parmesan cheese whey and counted by a molecular approach based on Random Amplified Polymorphic DNA (RAPD) fingerprinting. Results showed interactions among the three lactobacilli as confirmed by comparison of growth kinetics and pH behaviour of the respective strains in mixed-strain culture with single-strain cultures. The present work underlines the importance of noting strain-to-strain interactions among thermophilic lactobacilli in whey co-cultures.

A simple and specific method using a Dionex carbohydrate analyser was developed for the estimation of galactose in Parmesan cheese. This method could also be applied for the determination of other monosaccharides present in any dairy product which is amenable to aqueous extraction. Conditions were also established for the removal of proteins and other interfering materials from the aqueous extracts by using SCX columns. The method is not only highly selective, but also extremely sensitive, with the detection limit for sugars being in the nmol range. Moreover, automation of the analytical procedure can be achieved easily by the use of an autosampler which allows analysis of a large number of samples with minimal effort.

An inexpensive chromogenic enzymatic detection system was developed for the assay of lactose in foods using a microassay format. This assay system is based on the actions of two substrate-specific enzymes, lactase and glucose oxidase; which, when combined in a buffered solution of iodide, molybdate and polyvinyl alcohol, produce a coloured iodine-polyvinyl alcohol complex in the presence of lactose. The enzymatic reactions were performed in the wells of a microtitre plate and measured using a microtitre plate reader. The enzymatic detection system exhibited a linear dose-response relationship with respect to lactose concentration. The application of this detection system as a screening method for lactose in grated parmesan cheese samples is demonstrated.

Three batches each of Parmesan and mozzarella cheese were prepared, using milk which was naturally contaminated with aflatoxin M1. These cheeses were analyzed for aflatoxin M1 content at intervals while Parmesan was ripened for 43 weeks or mozzarella was stored for 17 weeks. There was a 5.8-fold enrichment of AFM1 in the Parmesan cheese over that in the milk from which the cheese was made. Apparent levels of aflatoxin M1 in Parmesan cheese started high, decreased until about the 22nd week of age and then slowly increased until the cheese was 43 weeks old, but the final concentration was less than that found initially. There was an 8.1-fold enrichment of AFM1 in mozzarella cheese over that in the milk from which it was made. Levels of aflatoxin M1 in mozzarella cheese varied slightly but remained near initial concentrations throughout the storage period.