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- 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.
- Sweet whey cheese matrices inoculated with the probiotic strain Lactobacillus paracasei LAFTI® L26Publication . Madureira, Ana Raquel; Soares, José Carvalho; Pintado, M. E.; Gomes, Ana M. P.; Freitas, A. C.; Malcata, F. XavierConsumption of dairy products containing viable probiotic strains has increased dramatically in recent years, owing to general health claims associated therewith. This trend has boosted diversification of the portfolio of said products, including whey cheese matrices. However, taking into account the relatively poor organoleptic and textural features of these matrices, improvement is in order via incorporation of selected additives, provided that viability of the strains is duly assayed. Lactobacillus paracasei LAFTI® L26 was accordingly incorporated into whey protein solid matrices, in the presence of several additives aimed at enhancing their organoleptic appeal and textural performance. These matrices were produced from a combination of either ovine or bovine whey (or a mixture thereof) with ovine milk, and were inoculated at 10% (v/v) with the probiotic strain. Sugar, sugar and aloe vera, sugar and chocolate, and sugar and jam were further added, and the resulting products were then stored at 7 ◦C for 21 d. In general, viable cell numbers remained high in all experimental matrices throughout storage. Despite the observed low extents of breakdown, proteolytic activities by the end of storage were higher in matrices containing jam. Furthermore, L. paracasei partially converted lactose into lactic acid in these matrices. Additives enhanced the organoleptic features of whey cheeses, and produced different textural patterns. The higher sensory scores were attained by matrices containing sugar: sugar and aloe vera received the best scores by 3 d of storage, but these scores decreased as storage time elapsed.
- Influence of bacterial dynamics upon the final characteristicsPublication . Pereira, Cláudia I.; Graça, João A.; Ogando, Natacha S.; Gomes, Ana M. P.; Malcata, F. XavierThe microbiological profile in raw milk cheeses is typically characterized by a multitude of microbial groups, with interactions among them throughout ripening that are not fully understood to date. Incidence of undesired microorganisms in raw cheesemaking milk, as is the case of either spoilage or even pathogenic ones, is a common trait in Portuguese traditional cheeses. Hence, they will likely contribute to the physicochemical changes occurring therein and, consequently, to the characteristics of the final product. In order to gain insight into their role, model cheese systems, manufactured as far as possible according to artisanal practices (except that the initial microbial load and biodiversity were controlled), were experimentally tested. Single contaminants, or a consortium thereof, were inoculated at two levels in sterilized raw ewe's milk, and duly combined with inocula containing one or two lactic acid bacteria normally found in those traditional cheeses. The physicochemical composition, organic acid profile, and evolution of both protein breakdown and rheology were monitored throughout a 60 d-ripening period. Modifications brought about within the cheese matrix as a result of microbial metabolism, especially those arising from the interaction between lactic acid bacteria and unwanted microorganisms, included the enhanced release of peptides and free amino acids, which in turn led to higher viscoelastic moduli. The final model cheeses could be well discriminated, based on the impact of the various inocula considered upon the levels of organic acids. Conversely, proteolysis and viscoelastic properties appeared to be essentially independent of the initial microflora.