F.C. Ibáñez

Formation of biogenic amines in Idiazabal ewe's-milk cheese: effect of ripening, pasteurization, and starter

The importance of biogenic amines stems from their toxicity and their potential as a cause of food poisoning. After fish, cheese has been the foodstuff most often responsible for cases of food poisoning caused by ingestion of biogenic amines. Changes in biogenic amine (histamine, tyramine, putrescine, cadaverine, tryptamine, isopentylamine, spermidine, and phenylethylamine) content during the ripening of a cheese made from raw ewes milk were studied, together with the effects of pasteurization and a commonly used commercial starter and indigenous starter cultures. Biogenic amines were determined by high-pressure liquid chromatography following extraction from the cheese and derivatization with dansyl chloride. Levels of histamine, potentially the most toxic amine, in the semihard Idiazábal cheese were very low. Tyramine, putrescine, and cadaverine were the main amines present in this type of cheese. Levels of those amines increased during ripening. Pasteurization of the milk brought about a reduction in the biogenic amine content of the ripened cheese, irrespective of the starter culture employed. The indigenous starter cultures considered in this study produced higher levels of histamine and cadaverine and lower levels of tyramine and putrescine than the commercial starter culture tested.

Seasonal changes in the composition of bulk raw ewe's milk used for Idiazabal cheese manufacture

Seasonal changes in the composition of bulk raw ewes milk used for Idiazabal cheese manufacture and its influence on the cheese yield are reviewed. This review is based on biochemical and microbiological data previously published on the composition of a bulk raw ewes milk collected at three different times of the year. In order to characterize, in a more extensive perspective, the seasonal changes in the composition of this bulk raw ewes milk and its influence on actual cheese yield, multivariate statistical analyses were applied to the compositional data of the milk and the actual cheese yield obtained at the factory. The results show pronounced seasonal changes in the composition of bulk raw ewes milk. Changes in cheese yield, lipolytic activity and microbiological quality of the bulk raw ewes milk are the principal aspects seasonally affected during the cheesemaking period. Also, the seasonal changes observed in the bulk raw ewes milk composition strongly affect the quality of Idiazabal cheeses manufactured over the cheesemaking period.

Evaluation of the effect of rennet type on casein proteolysis in an ovine milk cheese by means of capillary electrophoresis.

Capillary electrophoresis was used to study the evolution of casein throughout the ripening process of Roncal Denomination of Origin ewes milk cheese and to assess the type of rennet in its hydrolysis. Two manufactures were prepared, each with four vats; two of them had added lamb artisan rennet, batch A [clotting activity of 97.54 rennet units (RU) ml(-1)] and batch B [clotting activity of 16.26 RU ml(-1)]; one vat included calf industrial rennet, batch I (clotting activity of 45.70 RU ml(-1)); and the fourth vat had added mixed rennet, batch M, a 50:50 mixture of lamb (batch A) and calf (batch I) (clotting activity of 77.53 RU ml(-1)). The content of casein nitrogen in fractions alpha-casein1CE, alpha-casein2CE, beta-casein1CE and beta-casein2CE was quantified in cheese after 1, 15, 30, 60, 120 and 180 days of ripening. Beta-casein fractions undergo lesser degradation during the ripening time than alpha-casein proteins. The degradation of alpha-caseins is very much influenced by the clotting activity of the rennet used, so that the more active the clotting activity the greater the hydrolysis of those caseins. Nevertheless, it is at the level of beta-caseins that we observe the evidence of the influence of the type of rennet, thus noting a less intense proteolytic activity in the batch made with calf rennet, batch I.

Evolution of free amino acids during Idiazábal cheese ripening

Abstract As a contribution to knowledge of ripening ewes cheese, the evolution of free amino acids was studied over a year of the ripening period by reversed phase high performance liquid chromatography (RP-HPLC). Total free amino acid content during Idiazabal cheese ripening varied between 140 mg/100 g dry matter the first day and 1500 mg/100 g dry matter at one year. The major amino acids were: glutamic acid, leucine, valine, phenylalanine, lysine and alanine which approximately accounted for 50% of the total free amino acid content, probably indicating the preferential cleavage of peptide bonds by the proteolytic agents in the cheese. Non-protein amino acids such as ornithine, citrulline or γ-aminobutyric acid were also found in proportions near to 9% of the total free amino acids. Amino acids such as arginine, which is responsible for unpleasant tastes, or γ-aminobutyric acid, which is usually detected in low quality cheese, are present in very low concentrations in Idiazabal cheese.

Influence of rennet milk-clotting activity on the proteolytic and sensory characteristics of an ovine cheese

Abstract Roncal cheese (regulated by an Apellation of Origin) is a traditional hard cheese manufactured from raw ewes milk in the region of Navarre in Spain. Roncal cheeses, manufactured using two lamb rennets with different milk-clotting activity levels, were evaluated to compare their chemical, proteolytic, and sensory characteristics. A preliminary study of samples of lamb rennets indicated that a large proportion of such rennets did not fulfil current microbiological requirements and likewise revealed considerable variation in the milk-clotting activity of the samples examined. Trends in the overall physicochemical parameter values (pH, dry matter, fat, and protein) were similar in both cheese batches. Proteolysis of the nitrogen fractions was observed to take place at a faster rate in the cheeses made using the rennet with the higher milk-clotting activity (soluble nitrogen, non-protein nitrogen, and amino acid nitrogen values around 13–20% higher than in the cheeses made using the rennet with the lower milk-clotting activity after 180 days of ripening). Urea-PAGE electrophoretic analysis of the caseins from the cheeses manufactured using both types of rennet showed that the β-caseins were less susceptible to proteolysis than the α s -caseins. The effect of the different milk-clotting activity levels was most pronounced on the α s -caseins, in which the rennet with the higher milk-clotting activity gave higher breakdown. Nevertheless, the differences in the proteolysis rates did not yield any appreciable sensory differences.

Changes in the free amino acid content during ripening of Idiazabal cheese: influence of starter and rennet type

The effect of starter and rennet type on free amino acid release during ripening of Idiazabal cheese was studied. Four batches of cheeses were manufactured depending on the rennet used, commercial calf rennet or artisanal lamb rennet, and the addition or not of starter culture. Cheese samples contained 24 individual free amino acids Leu, Glu, Val and Phe showing the highest contents during the ripening. The results indicated that the release of the free amino acids during ripening was strongly affected by starter added to the cheeses, and that this effect varied markedly with the rennet used for cheesemaking. Total amounts of free amino acids were higher for the cheeses made with commercial calf rennet than for those made with artisanal lamb rennet, regardless of starter addition. Likewise, the highest total free amino acid levels were found in the cheeses made with starter, regardless of the type of rennet used.

Optimization of indirect parameters which affect the extractability of volatile aroma compounds from Idiazábal cheese using analytical supercritical fluid extractions (SFE)

Abstract Various sample preparation techniques and collection procedures for a supercritical fluid extraction (SFE) system were tested and compared. Special attention was paid to parameters which influence the extraction results, but are not part of the extraction process per se. The application of SFE to the extraction of the aroma components from unsmoked ewe’s milk Idiazabal cheese was undertaken for the first time. It was, therefore, necessary to optimize and validate the extraction conditions. The parameters which were optimized included sample preparation (lyophilization and sonication); sample to adsorbent ratio; reconstitution solvent; trap type and trapping temperature. The best extraction results were achieved for a comminuted cheese sample containing added alumina (1:1 ratio with cheese) as the adsorbent and n-hexane:acetone (2:1) as the reconstitution solvent, and a polar octadecylsilica (ODS) trap held at a temperature of −5°C to retain volatile compounds.

Casein breakdown during ripening of Idiazabal cheese: influence of starter and rennet type

The objective of this work was to determine the effect of starter and rennet type on casein breakdown during Idiazabal cheese ripening. Four batches of cheeses were manufactured with two rennets, commercial calf rennet and artisanal lamb rennet, and the use of natural flora or a commercial starter. Electrophoretic analysis of cheese samples showed six bands identified as αs1-, αs2 + β-, αs1-I-, γ1-, β-I- and para-κ-casein. As expected, the casein breakdown during cheese ripening was considerably affected by rennet type and the use of a commercial starter. The artisanal lamb rennet produced a higher hydrolysis of casein fractions than the commercial calf rennet, probably owing to its high percentage of chymosin (around 78%). The effect of addition of starter on proteolysis was dependent on the casein fractions generated by artisanal lamb rennet or commercial calf rennet. © 2000 Society of Chemical Industry

Effect of ewe's-milk pasteurization on the free amino acids in Idiazábal cheese

Abstract This study compared the use of raw and pasteurized milk in the manufacture of Idiazabal ewes-milk cheese. Two indigenous starters, A and B were tested in an attempt to find a starter culture potentially capable of developing the typical characteristics of Idiazabal cheese traditionally made from raw milk while using pasteurized milk. The nitrogen fractions and free amino acids were analysed over the ripening period. Pasteurization caused a considerable decrease in amino acid release in the cheese during ripening as reflected by the levels of non-protein–nitrogen and total free amino acids with starter A, but not when starter B was used. Multivariate analysis confirmed increases in asparagine, serine, and taurine and decreases in aspartic acid and glycine with pasteurization, irrespective of the starter used. The changes recorded in the levels of certain amino acids may be directly or indirectly responsible for the atypical sensory characteristics of the cheeses. Pasteurization of the milk for the manufacture of Idiazabal cheese is not recommended with either of the two starters tested.

Note. Effect of brining time on proteolytic changes in Idiazábal cheese during ripening / Nota. Cambios proteolíticos durante la maduración del queso Idiazábal por efecto del tiempo en salmuera

Idiazábal cheeses were made employing brining times of 12 h (batch A) and 36 h (batch B). Proteolytic changes in both batches were examined over 270 d of ripening; proteolysis was low in both batches, but lower in batch B than in batch A. Electrophoretic analysis revealed incom plete breakdown of αs and β-caseins at the end of the ripening period, particularly in batch B. The proportion of soluble nitrogen as a percentage of total nitrogen was 17.55% in batch B and 19.48% in batch A, while the proportion of non-protein nitrogen was 11.78% in batch B and 15.16% in batch A. The proportion of non-protein nitrogen as a percentage of soluble nitrogen was 67.17% in batch B and 77.88% in batch A. The free amino acids, the smallest non-protein nitrogen frac tion, attained values of 1203 mg/100 g of dry matter in batch B and 1902 mg/100 g of dry matter in batch A. After 60 d of ripening, the main free amino acids were glutamic acid, valine, leucine, lysine, and phenylalanine in both batches, although levels were higher in the batch with the shorter brining time. There was no clear trend in the non-protein-forming amino acids with either ripening time or brining time.