Biochemical changes in Picón Bejes-Tresviso cheese,a Spanish blue-veined variety,during ripening

The changes in the gross chemical composition, physico-chemical parameters, nitrogen fractions, caseins and their degradation products, and some fat characteristics were studied during the ripening process of 10 batches of Picón Bejes-Tresviso cheese, a traditional blue-veined variety made in the north of Spain. The values of the different compositional and physico-chemical parameters at the end of ripening did not differ very much from those found in other Spanish and European blue-veined cheeses. The total soluble nitrogen and the non-protein nitrogen increased by factors of 5.4 and 8, respectively, at the end of ripening compared to the values found in cheese curd after salting. The final values of all the nitrogen fractions showed that Picón Bejes-Tresviso cheese undergoes extensive and in depth proteolysis. The intense degradation of the caseins during ripening was confirmed when the caseins and their degradation products were quantified using PAGE techniques. The autooxidation of the fat does not seem very important during the ripening of this cheese. Nevertheless, lipolysis was very intense; the acidity index of the fat values (free fatty acid contents) increased by a factor of about 20 during ripening.     

Microbiological and biochemical changes during ripening of salchichón,a Spanish dry cured sausage

Development of the microflora and changes in the lipid and protein fractions during the ripening of salchichón, a kind of Spanish dry cured sausage, were studied. A commercial mixture of Pediococcus pentosaceus andMicrococcus varians was used as starter culture. Total aerobic bacteria, lactic acid bacteria, Micrococcaeae, Staphylococcus aureus, Entero-bacteriaceae , sulphite reducer Clostridium , yeasts and moulds were determined. The sarcoplasmic and myofibrillar solubility, denaturation and proteolysis index, parameters related to fat stability and the free fatty acid composition were analysed throughout the curing process: after mincing, after the fermentation stage, after the 2nd week of drying and in the final product (4th week of drying). The major changes in the characteristics of salchichón took place during the fermentation stage. This was due to proteolysis and lipolysis phenomena derived from high counts of lactic acid bacteria and Micrococcaeae in this stage. These changes were shown in the increase of the total free amino acid content, the peroxide index and the carbonyl compound content, and in the decrease of the protein solubility and the percentage of polyunsaturated free fatty acids, thus achieving the organoleptic characteristics of the final product.     

Study of Enterobacteriaceae during the manufacture and ripening of San Simón cheese

The aim of this work was to study the evolution of the population of Enterobacteriaceae in one of the traditional Spanish cheeses, San Simón cheese, during the manufacture and ripening processes and its interrelation with the changes in some physico–chemical parameters.The evolution of the Enterobacteriaceae counts (VRBGA medium) and coliform counts (VRBA medium) was studied from samples of milk, curd and inner and surface zones of the cheese at different stages of ripening from five batches of traditionally manufactured artisan cheese. The counts obtained were very similar in both media and in general one log unit higher in the inner portion of the cheeses than on the surface.TheEnterobacteriaceae counts in milk were 10²–10³cfu g⁻¹and the counts increased during the first week of ripening reaching 10⁶–10⁷cfu g⁻¹in the inner portion of the cheese. From this time onwards, the counts slowly decreased to the end of ripening without disappearing completely.The most abundant species in the milk were Klebsiella oxytoca (36% of the isolated strains), Enterobacter cloacae (24%) and Klebsiella pneumoniae (20%). Escherichia coli, constituted the dominant species from the inner portion of the cheeses at the end of ripening (56% of the isolated strains), followed by Hafnia alvei (44%). However, in the samples of the surface portion of the cheese the dominant species at the end of ripening were K. oxytoca (40%), H. alvei (35%) and E. cloacae (20%).     

Changes in the volatile fraction during ripening of Mahón cheese

Mahón cheeses, manufactured in the Island of Minorca (Spain), were produced and ripened under controlled conditions. Cheeses were sampled and analyzed at different stages of ripening. Twenty-one major aroma components were identified. It was observed that, during ripening until the most commercially valuable product was obtained, (60–90 days) only 16 compounds varied significantly with time: butanoic, isovaleric, hexanoic, octanoic and decanoic fatty acids (p<0.001), together with heptanoic acid (p<0.005), 2-methyl pentanone, 2-methyl heptanone, 2-methyl nonanone, methyl ketones (p<0.001), ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl tetradecanoate, ethyl hexadecanoate and ethyl esters (p<0.001). These changes could be described by means of zero order kinetics. Through a PCA analysis it was found that three factors explained ca. 87% of the total variance. According to the first two components the variables were grouped by their chemical characteristics (fatty acids, methyl ketones, ethyl esters) and the cases by their ripening time (0/18 days, 35 days, 53/67/82 days).     

Characterisation by SPME–GC–MS of the volatile profile of a Spanish soft cheese P.D.O. Torta del Casar during ripening

The volatile profile of the Spanish soft cheese of the Protected Designation of Origin (PDO) Torta del Casar, made from raw ewes’ milk, was studied in four different stages of ripening (1, 30, 60 and 90 days) by the method of SPME–GC–MS. A total of 46 compounds were detected: 13 acids, 9 esters, 4 ketones, 7 alcohols, 3 aldehydes, 7 aromatic compounds and 3 compounds which could not be classified into those groups. Carboxylic acids were the most abundant group isolated; their levels significantly increased during ripening and comprised 61.5% of the total aroma extract at the end of ripening. At day 90, acids of microbial origin were the most abundant, followed by acids derived from amino acids while acids from lipolysis of triglycerides were the least abundant. Esters were the next most important group and their amount also increased significantly during maturation, as did ketones, while alcohols content slightly decreased at the end of the ripening. At day 90, the compounds at highest levels were acetic acid, 3-methylbutanoic acid, butanoic acid propyl ester and 2-butan-one; so these compounds, due to their high levels and their low threshold value could play an important role in the final aromatic profile of this cheese.     

Development of volatile compounds during the manufacture of dry-cured "lacón," a Spanish traditional meat product

Volatile compounds were determined throughout the manufacture of dry-cured "lacón," a traditional dry-salted, and ripened meat product made in the north-west of Spain from the foreleg of the pig following a similar process to that of dry-cured ham. Volatiles were extracted by a purge-and-trap method and analyzed by gas chromatographic/mass spectrometry. One hundred and two volatile compounds were identified. In raw material, only 34 volatile compounds were found and at very low levels. The number of volatile compounds increased during processing. The substances identified belonged to several chemical classes: aldehydes (23), alcohols (9), ketones (15), hydrocarbons (37), esters (4), acids (3), furans (4), sulphur compounds (1), chloride compounds (1), and other compounds (4). Results indicated that the most abundant chemical family in flavor at the end of the manufacturing process was aldehydes, followed by hydrocarbons and ketones. Lipids were the most important precursor of flavor compounds of dry-cured "lacón."     

Biogenic amine content during the manufacture of dry-cured lacón, a Spanish traditional meat product: Effect of some additives

The content of nine biogenic amines (agmatine, tryptamine, 2-phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine and spermine) was determined throughout the manufacture of dry-cured lacón, a traditional dry-salted and ripened meat product made in the north-west of Spain from the fore leg of the pig following a similar process to that of dry-cured ham. The effect of the use of additives (glucose, sodium nitrite, sodium nitrate, sodium ascorbate and sodium citrate) on the biogenic amine content during manufacture was also studied. Tryptamine and spermine were the main biogenic amines in fresh meat, while tryptamine and cadaverine were the most abundant at the end of the manufacturing process. During ripening the total amine content increased significantly (P<0.05) in the batches made both without and with additives. The use of additives significantly (P<0.05) increased the total amine content and the content of tryptamine, tyramine and histamine. The total biogenic amine content at the end of the manufacturing process was low as expected for a product in which there is little active microbial metabolism during manufacture.     

Does smearing inoculum reflect the bacterial composition of the smear at the end of the ripening of a French soft, red-smear cheese?

The microbial community composition and dynamics during the production of a French soft, red-smear cheese were investigated. The colonization efficiency of the smearing inoculum was followed, and the parts played by the inoculum used and the resident microflora were tentatively estimated. Single-strand conformation polymorphism analysis (SSCP) was applied to 2 productions of a soft, red-smear cheese produced by the same dairy plant at 4-mo intervals. Microbial composition of the different cheese samples analyzed was found to be reproducible from one production to another. However, the composition of the surface flora of both cheeses at the end of the ripening did not reflect the composition of the smearing inoculum used, qualitatively as well as quantitatively. These results were confirmed by those obtained when assessing the microbial composition of the culturable flora by the spread plate technique. The inoculum used by the industry had low resiliency potentialities against colonization of cheeses by resident organisms. Therefore, fitness and colonization potential of smearing inocula should be carefully assessed by the industry before use. The use of Arthrobacter strains as part of the smearing inoculum should be evaluated.     

Technological characterization of lactic acid bacteria isolated from Armada cheese (a Spanish goats’ milk cheese)

Thirty-one strains of lactic acid bacteria (LAB) isolated from Armada cheese, Sobado variety, (eight strains of Lactococcus lactis subsp. lactis, four strains of Lactococcus lactis subsp. cremoris, two strains of L. lactis subsp. lactis biovar. diacetylactis, two strains of Leuconostoc mesenteroides subsp. mesenteroides, two strains of Leuconostoc mesenteroides subsp. dextranicum, five strains of Lactobacillus plantarum, six strains of Lactobacillus casei subsp. casei and two strains of Lactobacillus brevis) were screened for their acidifying capacity and enzymatic activity, that included the rapid API-ZYM system, the proteolytic activity, the amino-, di-, and carboxypeptidase activity and the caseinolytic activity. The strains of L. lactis subsp. lactis exhibited the highest acidifying and proteolytic activity. Lipase and esterase activity was practically non-existent for lactococci and lactobacilli; a certain esterase activity was observed among leuconostoc. The highest aminopeptidase activity was demonstrated by the cell-free extract (CFE) of some strains of L. plantarum, L. casei subsp. casei and L. mesenteroides subsp. dextranicum. The CFEs of L. lactis subsp. cremoris and L. lactis subsp. lactis possessed carboxypeptidase and dipeptidase activities, at levels depending on the strain. Appreciable caseinolytic activity was detected for the CFE of L. plantarum and those some lactococci.     

Microbiological and biochemical changes in the traditional fermentation of soybean for ‘soy-daddawa’ — Nigerian food condiment

The traditional production of ‘daddawa’ from the fermentation of soybean involves predominantly Bacillus species notably B. subtilis, B. licheniformis and B. pumilus. AlthoughMicrococcus luteus and Staphylococcus epidermidis were present in relatively low numbers at the onset of fermentation, they do not appear to play any major role in the fermentation process. The bacterial population, pH and moisture content increased with fermentation. The titratable acidity increased in the first 24 h and then dropped as fermentation progressed. Amylase activity increased rapidly with fermentation attaining a peak at 48 h with a concomitant decrease in total soluble sugar level while the reducing sugar increased in the first 24 h and dropped. Protease activity also increased rapidly in the first 36 h and dropped giving higher amounts of free amino acids with fermentation. Lipase and Beta-fructofuranosidase activities were minimal in the fermenting seeds.     

Use of PCR-based methods and PFGE for typing and monitoring homofermentative lactobacilli during Comté cheese ripening

In order to obtain a better understanding of the biochemical events taking place in Saccharomyces cerevisiae during the lag phase, the proteins expressed during the first hours after inoculation were investigated by two-dimensional (2-D) gel electrophoresis and compared to those expressed in late respiratory growth phase. The studies were performed on a haploid strain (S288C) grown in defined minimal medium. Some of the abundant proteins, whose expression relative to total protein expression was induced during the lag phase, were identified by MALDI MS, and the expression of the corresponding genes was assessed by Northern blotting. The rate of protein synthesis was found to increase strongly during the lag phase and the number of spots detected on 2-D gels increased from 502 spots just after inoculation to 1533 spots at the end of the lag phase. During the first 20 min, the number of detectable spots was considerably reduced compared to the number of spots detected from the yeast in respiratory growth just prior to harvest and inoculation (747 spots), indicating an immediate pausing or shutdown in synthesis of many proteins just after inoculation. In this period, the cells got rid of most of their buds. The MALDI MS-identified, lag phase-induced proteins were adenosine kinase (Ado1p), whose cellular role is presently uncertain, cytosolic acetaldehyde dehydrogenase (Ald6p) and (DL)-glycerol-3-phosphatase 1, both involved in carbohydrate metabolism, a ribosomal protein (Asc1p), a fragment of the 70-kDa heat shock protein Ssb1, and translationally controlled tumour protein homologue (Yk1056cp), all involved in translation, and S-adenosylmethionine synthetase I involved in biosynthesis reactions. The level of mRNA of the corresponding genes was found to increase strongly after inoculation. By pattern matching using previously published 2-D maps of yeast proteins, several other lag phase-induced proteins were identified. These were also proteins involved in carbohydrate metabolism, translation, and biosynthesis reactions. The identified proteins together with other, yet unidentified, lag phase-induced proteins are expected to be important for yeast growth initiation and could be valuable biological markers for yeast performance. Such markers would be highly beneficial in the control and optimisation of industrial fermentations.     

Formation of the aroma of a raw goat milk cheese during maturation analysed by SPME–GC–MS

The volatile profile of the Spanish goat raw milk cheese of the protected designation of origin (PDO) “Queso Ibores” was studied at four stages of maturation (day 1, 30, 60, and 90) by the method of solid-phase micro-extraction–gas chromatography–mass spectrometry (SPME–GC–MS) to determinate the characteristic volatile compounds of this cheese and to know the changes in the volatile profile of this cheese during maturation. According to the PDO, Ibores cheese aroma varies between sweet and mild and it has a strong taste, slightly tart. A total of 64 compounds were detected: 14 acids, 18 alcohols, 13 esters, 6 ketones and 13 compounds which could not be classified in these groups. Carboxylic acids were the most abundant volatile compounds in the headspace of Ibores cheese. Content of volatile compounds was significantly modified (P < 0.05) during ripening. The relative total amounts of acids, esters and ketones increased during the first 60 days of maturation. The most characteristic compounds of Ibores cheese aroma were butanoic, hexanoic and octanoic acids, some alcohols (2-butanol and 2-heptanol), ethyl esters of hexanoic and butanoic acids, some methyl ketones (2-butanone, 2-pentanone and 2-heptanone) and δ-decalactone.     

Formation of alanine, α-aminobutyrate,acetate, and 2-butanol during cheese ripening by Pediococcus acidilactici FAM18098

There is limited information about the contribution of Pediococcus acidilactici, a nonstarter lactic acid bacteria, to cheese ripening and flavour development. Model Tilsit-type and Gruyère-type cheeses were produced using P. acidilactici FAM18098 as an adjunct. The adjunct did not influence the cheese manufacturing processes. The pediococcal log counts ranged from 7.0 to 8.0 cfu g⁻¹ after 90 and 120 days of ripening. P. acidilactici produced ornithine, a result of arginine metabolism by the arginine deiminase pathway, and α-aminobutyrate and alanine while simultaneously metabolising serine and threonine. The analysis of the volatile compounds in the cheeses showed that higher acetate, 2-butanone, and 2-butanol levels and lower diacetyl levels were present in the cheeses produced with P. acidilactici than in the control cheeses. The study illustrates that P. acidilactici can influence amino acid metabolism in cheese; further, ornithine, α-aminobutyrate, and acetate can serve as indicators for the presence of this species.     

Characterisation of the microflora of attiéké, a fermented cassava product, during traditional small-scale preparation

Attiéké is a fermented cassava product consumed mainly in Cote d'Ivoire. The aim of this study was to characterise the attiéké fermentation by examining products from 15 small-scale production sites at various stages of its preparation. For the preparation of attiéké, fresh cassava is grated to a pulp and inoculated with 10% of a spontaneous traditional inoculum. The inocula contained aerobic mesophiles at mean numbers of 8.2 x 10(7) cfu/g and lactic and acetic acids at mean concentrations of 0.2% and 0.1%, respectively. The mean pH was 5.0. Lactic acid bacteria were the dominant microorganisms in cassava pulp throughout fermentation with the mean numbers being 1.2 x 10(9) cfu/g after 15 h. The identification to the species level of microorganisms from one representative attiéké production of good quality showed that, at the start of fermentation, Leuconostoc mesenteroides subsp. mesenteroides was present in the highest numbers, accounting for 20% of all lactic acid bacteria. As the fermentation proceeded, this species was replaced by homofermentative lactic acid bacteria, Lactobacillus salivarius and Lactobacillus delbrueckii subsp. delbrueckii, present at 20% and 16%, respectively, and obligate heterofermentatives, Lactobacillus fermentum and Lactobacillus confusus at 12% and 10%, respectively, of total lactic acid bacteria in the flora at the end of fermentation. High numbers of acid-sensitive microorganisms, Bacillus circulans, Bacillus lentus, Enterobacter sakazakii, Enterobacter cloacae and Klebsiella pneumoniae subsp. pneumoniae, were transferred to the pulp in the inocula, but acidification to a mean pH of 4.4 with mean lactic and acetic acid concentrations of 0.59% and 0.2%, respectively, prevented their growth and reduced their numbers to less than 10(2) cfu/g at the end of fermentation. The mean numbers of Candida tropicalis, the main yeast present, remained relatively constant at about 10(5) cfu/g throughout attiéké production. The mean numbers of aerobic mesophiles decreased to below 10(2) cfu/g as a result of the steaming process. The finished attiéké had a mean pH of 4.4 and mean lactic and acetic acid concentrations of 0.6% and 0.1%, respectively.     

Characterisation of a traditional Finnish liver sausage and different types of Spanish liver pâtés: A comparative study

The physico-chemical characteristics of a traditional Finnish liver sausage (FLS) and different types of Spanish porcine liver pâtés (commercial, home-made and experimental) were studied. The characteristic recipes and different protocols of manufacture influenced the chemical composition and oxidative stability of the liver products. FLS showed, amongst the liver products, the smallest percentage of monounsaturated fatty acids (MUFAs) and the highest of polyunsaturated fatty acids (PUFAs) acids, including long-chain PUFAs. From a nutritional point of view, the FLS showed the smallest n − 6/n − 3 value whereas the experimental liver pâté (ELP) presented the smallest ratio between hyper- (lauric, myristic and palmitic acids) and hypocholesterolemic fatty acids (oleic and linoleic acids). A large variety of volatile compounds were isolated from the liver products including lipid-derived volatiles, Strecker aldehydes and alcohols, sulphur and nitrogen containing compounds and volatile terpenes, providing information on their oxidative stability and aroma characteristics. The FLS presented a balanced profile between lipid-derived volatiles and volatile terpenes from spices. The presence of potent odorants from added flavourings in the commercial liver pâté (CLP) could mask undesirable aroma odours from a large variety of lipid-derived volatiles. The home-made liver pâté (HMLP) also presented large amounts of lipid-derived volatiles as a likely consequence of strong thermal treatment during cooking, the presence of high amounts of iron and the absence of sodium nitrites and ascorbate in its composition. The ELP showed the simplest profile due to its high oxidative stability and the absence of added spices.     

Effect of replacing pork backfat with pre-emulsified olive oil on lipid fraction and sensory quality of Chorizo de Pamplona - a traditional Spanish fermented sausage

Six treatments of Chorizo de Pamplona, traditional Spanish fermented sausage, were manufactured under usual commercial conditions by replacing 0, 10, 15, 20, 25 and 30% of pork backfat by pre-emulsified olive oil with soy protein isolate. Sausages with 20-30% replacing level had higher (P<0.05) protein content than control as a result of the addition of soy protein isolate. The oleic acid increased (P<0.05) in sausages with 15-30% replacing level, and linoleic acid increased in sausages with 10-25%. Sausages with 10-25% of substitution had lower total SFA-stearic and higher (P<0.05) total MUFA, total PUFA, (MUFA+PUFA)/(SFA-stearic), and PUFA/(SFA-stearic). Cholesterol content showed reduction about 12-13% in sausages with 20-25% replacing level, and up to 22% in sausages with 30% replacing level. Sausages with 10-25% of substitution were acceptable from the sensorial point of view. The texture and colour instrumental measures were comparable with that of commercial products. No increments in hexanal content were observed. It is concluded that up to 25% of pork backfat can be replaced with pre-emulsified olive oil in the production of Chorizo de Pamplona fermented sausages. Higher replacing levels of pork backfat did not show nutritional advantages in relation to the fatty acid profile and were unacceptable due to considerable dripping of fat during ripening.     

Monitoring and identification of bacteria associated with safety concerns in the manufacture of São Jorge, a Portuguese traditional cheese from raw cow's milk

The aim of this study was to assess the hygienic quality of raw milk used in the manufacture of S?o Jorge, a Protected Denomination of Origin Portuguese semihard cheese, as well as to ascertain the sanitary conditions prevailing during its processing. Viable counts of Enterobacteriaceae and Micrococcaceae were accordingly obtained, pertaining to 21 independent batches (including samples of raw milk, curd, and cheeses after 1, 3, and 4 months of ripening), from 7 dairy farms. Standard plate counts (log CFU per milliliter or per gram) ranged from 6.1 to 8.6 in raw milk, whereas they ranged from 7.0 to 8.0 in 4-month-old cheeses. Viable counts of Enterobacteriaceae ranged between 5.9 and 7.0 in raw milk and between 0.0 and 1.3 in 4-month-old cheeses. Species identified within this family encompassed Klebsiella oxytoca, Klebsiella cloacae, Klebsiella pneumoniae, Enterobacter sakazakii, and Escherichia coli; Klebsiella ornithinolytica, Klebsiella terrigena, and Serratia odorifera were detected only in raw milk. No Salmonella whatsoever could be detected in any of the samples. Viable counts of Micrococcaceae ranged between 4.7 and 5.9 and between 1.3 and 3.3 in raw milk and 4-month-old cheeses, respectively. Species identified within this family encompassed Staphylococcus sciuri, Staphylococcus epidermidis, Staphylococcus saprophyticus (which was found mainly in ripened cheeses), and Staphylococcus aureus (which was not detected in 4-month-old cheeses). Accompanying physicochemical analyses included determination of moisture, salt, and pH. Statistical analyses revealed a negative correlation between salt content and viable numbers of Enterobacteriaceae in cheese, whereas in the case of Micrococcaceae, a more negative correlation was found between viable numbers and moisture content than between viable numbers and pH. The results of our study indicate, in general, poor milk handling conditions in all farms, given that the indicators total mesophile and Enterobacteriaceae counts were high, between 100- and 1,000-fold those enforced by international standards pertaining to the matrices in question. However, by the time of regular consumption (i.e., after 4 months of ripening), S?o Jorge cheeses exhibit low levels of contamination by Enterobacteriaceae and S. aureus, as well as absence of Salmonella.     

Assessment of acrylamide intake of Spanish boys aged 11–14 years consuming a traditional and balanced diet

Acrylamide is a toxic and potentially cancer causing chemical formed in thermally treated foods, especially in carbohydrate rich. New dietary habits acquired by adolescents, increasing snacking and fast food consumption, lead to a high acrylamide intake, since the composition of these meals and their processing promote its appearance. This study investigated acrylamide daily exposure in a group of Spanish male adolescents (11–14 years) consuming a balanced diet based on their food preferences but reducing snacking and fast food, aimed to determine whether acrylamide exposure was reduced by the consumption of a traditional diet. Acrylamide content of main dishes was analyzed and input per serving calculated. The Spanish potato omelette and the grilled loin of pork with fried potatoes presented the highest levels of acrylamide (128 and 111 μg/kg respectively), followed by different meals also containing potatoes or cereal derived products. The acrylamide total intake was estimated at 0.534 μg/kg body weight/day, where the highest percentage was provided by the breakfast (31.66%), the afternoon snack being the lowest contributor (16.19%). These results indicate consumption of a balanced and traditional diet, besides the well known beneficial effects on health, can also moderate acrylamide exposure and thus its possible long-term toxicological effect.