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- Effect of high pressure pre-treatment on raw ewes’ milk and on subsequently produced cheese throughout ripeningPublication . Inácio, Rita S.; Pinto, Carlos A.; Saraiva, Jorge A.; Gomes, Ana M. P.BACKGROUND: Raw ewe’s milk, used to manufacture Serra da Estrela Protected Designation of Origin (PDO) cheese, was pre-treated by high pressure processing (HPP), using previously optimized conditions (121 MPa/30 min), in order to evaluate its effect on milk technological properties for subsequent cheese production, namely the impact on resulting curd, whey, and cheese throughout ripening. RESULTS: The cheese yield increase 10.4% as a result of milk pre-treated by HPP, which also yielded inactivation of beneficial microbial groups. After 60 days of ripening, both treated and control cheeses showed neither significant differences (P ≥ 0.05) in quantified microbial load nor in basic physicochemical quality parameters. CONCLUSION: HPP seems to be a promising non-thermal treatment for ewes’ milk to inactivate contaminant bacteria yet with no negative effect on lactic acid bacteria, which are very important for the unique characteristics of Serra da Estrela cheese.
- Serra da Estrela cheese: a reviewPublication . Inácio, Rita S.; Gomes, Ana M. P.; Saraiva, Jorge A.Serra da Estrela cheese with Protected designation of origin certification is manufactured using only raw ewes’ milk, salt, and a crude plant rennet, from the dried flowers of Cynara cardunculus L., resulting in a cheese with peculiar sensorial features (without the addition of starters or additives) that has existed over many centuries. More than 40 scientific reports concerning this cheese have been published since 1992. The composition and microbial profile have revealed certain variations among the literature. During the ripening of Serra da Estrela cheese, biochemical changes occur, which are reflected in its particular flavor and texture characteristics. An intense proteolytic activity takes place along ripening and storage, and volatiles are associated with typical flavor like “butter‐cream texture.” Innovation concerning Serra da Estrela cheese has been performed within milk quality, manufacture process, and in ripened cheese.
- The combined effect of pressure and temperature on kefir production - a case study of food fermentation in unconventional conditionsPublication . Ribeiro, Ana C.; Lemos, Álvaro T.; Lopes, Rita; Mota, Maria J.; Inácio, Rita S.; Gomes, Ana M. P.; Sousa, Sérgio; Delgadillo, Ivonne; Saraiva, Jorge A.Food fermentation under pressure has been studied in recent years as a way to produce foods with novel properties. The purpose of this work was to study kefir production under pressure (7–50 MPa) at different temperatures (17–32 °C), as a case study of unconventional food fermentation. The fermentation time to produce kefir was similar at all temperatures (17, 25, and 32 °C) up to 15 MPa, compared to atmospheric pressure. At 50 MPa, the fermentation rate was slower, but the difference was reduced as temperature increased. During fermentation, lactic and acetic acid concentration increased while citric acid decreased. The positive activation volumes (Va) obtained indicate that pressure decreased the fermentation rate, while the temperature rise led to the attenuation of the pressure effect (lower Va). On the other hand, higher activation energies (Ea) were observed with pressure increase, indicating that fermentation became more sensitive to temperature. The condition that resulted in a faster fermentation, higher titratable acidity, and higher concentration of lactic acid was 15 MPa/32 °C. As the authors are aware, this is the second work in the literature to study the combined effect of pressure and temperature on a fermentative process.