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- Manufacturing of fermented goat milk with a mixed starter culture of Bifidobacterium animalis and Lactobacillus acidophilus in a controlled bioreactorPublication . Kongo, J. M.; Gomes, Ana M. P.; Malcata, F. XavierAims: This work was undertaken to study the feasibility and the characteristics of a fermented product made of goat milk, using a mixed starter culture of Bifidobacterium animalis and Lactobacillus acidophilus under controlled conditions, and to determine their survival in the fermented milk during refrigerated storage. Methods and Results: Goat milk was inoculated with Lact. acidophilus and Bif. animalis mixed starter, fermented in a glass bioreactor with controlled temperature (37 C) and anaerobiosis, and monitored for growth and acidification. The fermented milk was then stored for 10 days under refrigeration, and monitored daily for starter microflora survival and pH changes. Lact. acidophilus viable counts reached a maximum of 7Æ1 · 108 colony-forming units (CFU) ml)1, and Bif. animalis a maximum of 6Æ3 · 107 CFU ml)1 by 20 h of fermentation. During refrigerated storage, both strains exhibited a good survival, with viable numbers remaining essentially constant throughout the experiment, whereas the pH of the fermented milk dropped slightly. Conclusions: Mixed cultures of Bif. animalis and Lact. acidophilus may be used to produce fermented goat milk with high counts of both probiotic strains. Significance and Impact of the Study: Goat milk fermented with Bif. animalis and Lact. acidophilus can be manufactured as an alternative probiotic dairy product.
- Antimicrobial Susceptibility of Enterococci Isolated from Terrincho CheesePublication . Pimentel, L. L.; Novais, C.; Pintado, M. E.; Gomes, Ana M. P.; Coque, T.; Sousa, J. C; Malcata, F. Xavier; Peixe, L.
- Survival of probiotic bacteria in a whey cheese vector submitted to environmental conditions prevailing in the gastrointestinal tractPublication . Madureira, A. R.; Pereira, C. I.; Truszkowska, K.; Gomes, Ana M. P.; Pintado, M. E.; Malcata, F. X.Various foods may be used to deliver probiotic bacteria into the gastrointestinal tract; one such example is Requeijão, a Portuguese whey cheese. Survival and stability of Bifidobacterium animalis strains BLC-1, Bb-12, and Bo, Lactobacillus acidophilus strains LAC-1 and Ki, L. paracasei ssp. paracasei strain LCS-1 and L. brevis strain LMG 6906 inoculated into Requeijão, when exposed to simulated gastrointestinal tract conditions, were assessed. Homogenates of inoculated whey cheese in 0.85% (w/v) sterile saline water were exposed to a solution of hydrochloric acid (pH 2.5–3.0) and pepsin (1000 unitsmL–1) at 371C, and then to 0.3% (w/v) bile salts after 60 or 120 min of acid exposure. All bacterial strains retained their initial viable cell numbers. Bifidobacterium animalis strains Bb-12 and Bo, and L. brevis strain LMG 6906 exhibited the highest viable cell numbers when exposed to bile salts, whereas the other strains had variable death rates.
- Viability of bifidobacterium la ctis and lactobacill us acidophilus in milk: sodium chloride concentration and storage temperaturePublication . Gomes, Ana M. P.; Teixeira, M. G. M.; Malcata, F. XavierThe growth and viability of Bifidobacterium lactis and Lactobacillus acidophilus per se and for both strains as a coculture were studied in reconstituted skim milk so as to assess their dependence upon temperature (5, I0 and 15C), NaCl concentration (0, 0.51 and 1.03 mol L-'), and storage time (0–8 weeks). Cultures of B. lads exhibited no signijkant loss of viability either with increasing NaCl concentration or increasing storage temperature within the ranges studied On the other hand, viability of L. acidophilus decreased with increasing temperature and increasing NaCl concentration under similar conditions. When cocultured with L. acidophilus, B. lactis was signiJicantly less tolerant to higher NaCl levels and higher temperatures than when in pure culture, although rial numbers were still above the threshold required for commercial application. Coculturing with B. lactis had no detrimental effect on viability of L. acidophilus. A mechanistic model, which considers the behavior of the pure and mixed microbial populations is described by specijic death rates which vary with temperature following Arrhenius relationships) and NaCl levels following simple inhibition kinetics) in the milk medium. Activation energies for the death rates of B. lactis and L. acidophilus were 14 kcal mot' and 9–15 kcal mol-I, respectively.
- Interrelationships among microbiological, physicochemical, and biochemical properties of Terrincho cheese, with emphasis on biogenic aminesPublication . Pinho, Olivia; Pintado, Ana I. E.; Gomes, Ana M. P.; Pintado, M. E.; Malcata, F. Xavier; Ferreira, Isabel M. P. L. V. O.Changes in the microbiological, physicochemical, and biochemical characteristics of Terrincho cheese as represented by native microflora, pH, water activity, soluble nitrogen fractions, free amino acids, and biogenic amines (e.g., ethylamine, dimethylamine, tryptamine, phenylethylamine, putrescine, cadaverine, histamine, tyramine, cystamine, and spermine) during ripening were monitored. Terrincho is a traditional Portuguese cheese manufactured from raw ewe's milk. The main groups of microorganisms (lactococci, lactobacilli, enterococci, pseudomonads, staphylococci, coliforms, yeasts, and molds) were determined following conventional microbiological procedures. Free amino acids and biogenic amines were determined by reverse-phase high-performance liquid chromatography, following extraction from the cheese matrix and derivatization with dabsyl chloride. The total content of free amino acids ranged from 1,730 mg/kg of dry matter at the beginning of the ripening stage to 5,180 mg/kg of dry matter by day 60 of ripening; such an increase was highly correlated with the increase of watersoluble nitrogen in total nitrogen, 12% trichloroacetic acid–soluble nitrogen in total nitrogen, and 5% phosphotungstic acid– soluble nitrogen in total nitrogen throughout ripening. Histamine was consistently present at very low levels, whereas putrescine, cadaverine, and tryptamine were the dominant biogenic amines and increased in concentration during ripening. Ethylamine, tryptamine, phenylethylamine, and cystamine reached maxima by 30 days of ripening and decreased thereafter. Significant correlations between amino acid precursors and corresponding biogenic amines, as well as between biogenic amines and microbial viable numbers, were observed.
- Development of a chemically defined medium for growth of bifidobacterium animalisPublication . Kongo, J. M.; Gomes, Ana M. P.; Malcata, F. X.The growth of Bifidobacterium animalis was tested, under batch and continuous culture conditions, for dependence upon specific nitrogen compounds. The addition of nitrogen bases (adenine, xantine, and guanine) to the medium containing acid-hydrolyzed casein significantly affected the growth of B. animalis, whereas no significant growth was reported when those bases were added to the medium containing only free amino acids; B. animalis was characterized by a μmax of 0.16/h when growth took place in PROLAB medium containing lactose and nitrogenous bases. Our study is potentially important toward design of improved infant milk formulations for healthy newborns.
- Caprine cheese with probiotic strains: the effects of ripening temperature and relative humidity on proteolysis and lipolysisPublication . Gomes, Ana M. P.; Silva, M. Luz P. C.; Malcata, F. XavierThe effects of ripening temperature, relative humidity and time on chemical and textural characteristics of a ‘probiotic’ goat’s milk cheese were examined. The experimental layout followed a 23 factorial design, with all possible combinations of 5 7C and 10 7C (ripening temperature), 85% and 95% (ripening relative humidity) and 1 day and 70 days (ripening time). All proteolytic indices measured (water-soluble nitrogen, trichloroacetic acid-soluble nitrogen and phosphotungstic acid-soluble nitrogen) were enhanced with increased ripening temperature to a greater extent than with increased ripening relative humidity; the increase in phosphotungstic acid-soluble nitrogen was the most significant. Free fatty acid concentrations in cheeses were not influenced by ripening relative humidity but increased with ripening temperature and time. A higher ripening temperature and a lower relative humidity gave rise to firmer cheeses. Postulated empirical models have provided a good fit to the experimental data set generated; such models were able to predict a decrease of 25 days in ripening time with no impairment of either proteolytic or lipolytic indices if a cheese were to be ripened at 10 7C (rather than 5 7C) and 95% relative humidity.
- Incorporation and survival of probiotic bacteria in whey cheese matricesPublication . Madureira, Ana R.; Gião, Maria S.; Pintado, Manuela E.; Gomes, Ana M. P.; Freitas, A. Cristina; Malcata, F. XavierThe viabilities of probiotic strains of Lactobacillus acidophilus, Lactobacillus paracasei, Bifidobacterium animalis, and Lactobacillus brevis were studied following incorporation in a whey cheese matrix. Experimental production of plain, as well as sugar-added or salt-added whey cheeses, was based on the traditional manufacture protocol of Requeijäo, a Portuguese whey cheese that essentially results from protein denaturation via heating of whey at about 85°C. After inoculation, the experimental whey cheeses were incubated at 7°C for 28 d. Our results have shown that all strains considered were able to maintain (or even increase) their initial viable numbers; L. paracasei ssp. paracasei strain LCS-1 and L. acidophilus strain Ki exhibited the highest cell viability in plain Requeijão by the end of the storage period—an increase of ca. 2 log cycles in their viable numbers was actually recorded. Among the parameters studied, bacterial species and matrix nature had the most important effect upon viable counts, whereas time of storage was the least important.
- Study of virulence factors in Enterococci isolated from cheesePublication . Pimentel, L. L.; Semedo, T.; Gomes, Ana M. P.; Pintado, M. E.; Tenreiro, R.; Crespo, M. T. B.; Malcata, F. Xavier
- Acidifying and aromatic properties of enterococcus strains in ovine and bovine milksPublication . Pimentel, L. L.; Soares, J. C.; Pintado, M. E.; Pintado, Ana I. E.; Gomes, Ana M. P.; Ferreira, A. C.; Malcata, F. X.
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