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- 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.
- Caseins as source of bioactive peptidesPublication . Silva, Sofia V.; Malcata, F. XavierBiologically active peptides are of particular interest in food science and nutrition because they have been shown to play physiological roles, including opioid-like features, as well as immunostimulating and anti-hypertensive activities, and ability to enhance calcium absorption. Hidden or inactive in the amino-acid sequence of dairy proteins, they can be released or activated in vivo during gastrointestinal digestion, or upstream during food processing via specific, enzyme-mediated proteolysis. Caseins, in either milk or dairy products (e.g. cheese), are important sources of those peptides; their biological significance, their impact on human health and the manufacture of novel functional food ingredients therefrom have been subject to intensive research, which will be briefly presented and critically discussed in this review.
- Relationships between flavour and microbiological profiles in Serra da Estrela cheese throughout ripeningPublication . Dahl, Stefan; Tavaria, Freni K.; Malcata, F. XavierCheeses manufactured in certi"ed dairies in the Portuguese region of Serra da Estrela, using refrigerated and non-refrigerated raw sheep milk, were quantitatively evaluated in terms of indigenous micro#ora and volatile compounds during a ripening period of up to 6 mo. Viable counts were obtained for lactococci, lactobacilli, leuconostoc, enterococci, yeasts, Enterobacteriaceae and staphylococci; analyses of volatiles were performed by chromatography after solid-phase micro-extraction. Treatment of all analytical data produced by principal component analysis revealed correlations between the major microbial groups present in cheese and patterns of volatiles generated. End products resulting from the degradation of sugars, free amino acids and glycerides constituted the predominant volatiles of Serra da Estrela cheeses. Among volatile, short-chain carboxylic acids detected were acetic, propionic, iso-butyric and iso-valeric acids; these compounds are known to be breakdown products of Gly, Ala and Ser, of Thr, of Val, and of Ile, respectively, following oxidative deamination. Semi-volatile fatty acids and their corresponding ethyl esters appeared in the cheese, probably as a result of the activity of lipases produced by yeasts and Enterobacteriaceae. These ethyl esters, which are responsible for fruity #avours, were especially pronounced in cheeses manufactured from refrigerated milk.
- An important source of coagulating enzymes for cheesemaking: uses of Cynara cardunculus L.Publication . Malcata, F. Xavier; Silva, Sofia V.
- Comparative studies on the gelling properties of cardosins extracted from Cynara cardunculus and chymosin on cow's skim milkPublication . Silva, Sofia V.; Allmere, Toomas; Malcata, F. Xavier; Anders; A.A comparative study was developed on the clottingactivities and gelling properties of cardosins A and B, extracted from dried flowers of Cynara cardunculus, and chymosin on cow’s skim milk, at various pH values. The determination of the total milk-clotting activity was performed followingan international standard, whereas a rheometer was employed to measure the viscoelastic properties of the gels subsequently formed: the evolution of the complex modulus (G ) and the phase angle (d) was monitored with time. The G values of the milk gels were higher for cardosins than for chymosin at pH 6.6, but the reverse held at pH 6.4 and 6.2. The d values were identical for all three enzymes tested. Chymosin exhibited the highest specific milk clotting activity, followed by cardosin B. The clottingactivity of chymosin seems to be more influenced than that of cardosins by the pH of milk.
- Flavour development via lipolysis of milkfats: changes in free fatty acid poolPublication . Regado, Mafalda A.; Cristóvão, Betina M.; Moutinho, Carla G.; Balcão, Victor M.; Aires-Barros, Raquel; Ferreira, João Paulo M.; Malcata, F. XavierUnder the trade name lipolysed milkfat (LMF), concentrated cheese flavours obtained via enzymatic treatments of cheese (or other dairy substrates) have been made available in increasing numbers. In this research effort, (anhydrous) milkfats from cows, ewes and goats were used as substrates for production of cheesy flavours. Those milkfats were subjected to modifications brought about by ten different (commercial) lipases and one cutinase, and the free fatty acids released were analysed by high performance liquid chromatography. Both the degrees of hydrolysis and the free fatty acid profiles of the final products were similar to those reported for several LMF products, although specific keynotes could be pinpointed. Consequently, those milkfats may represent alternative raw materials for manufacture of cheesy flavours, while contributing to alleviate the problem derived from the increasing surplus of milkfat in Western countries.
- Effect of dairy farm and milk refrigeration on microbiological and microstructural characteristics of matured Serra da Estrela cheesePublication . Tavaria, Freni K.; Reis, Patrícia J.M.; Malcata, F. XavierThis work was aimed at enumerating the viable microorganisms in ripened Serra da Estrela cheeses, manufactured from both refrigerated and non-refrigerated milk, in various dairies located throughout the demarcated region. Scanning electron microscopy was used to analyze the microstructure, and thus aid in understanding possible differences in their microbiological profile. The cheeses were allowed to ripen under controlled conditions, and sampled at 60, 90, 120, 150 and 180 d following manufacture. Viable numbers of lactic acid bacteria, staphylococci, Enterobacteriaceae and yeasts were obtained following standard plate counting on a number of selective media. Lactococcus was the most abundant genus (above 108 cfu g 1 of cheese) up to 120 d of ripening. No significant microstructural differences were observed in cheeses manufactured in different dairies over the ripening process. However, microstructural differences were apparent between cheeses manufactured with refrigerated versus non-refrigerated milk. r 2005 Elsevier Ltd. All rights reserved.
- The potential effect of FOS and inulin upon probiotic bacterium performance in curdled milk matricesPublication . Rodrigues, Dina; Rocha-Santos, Teresa A. P.; Pereira, Cláudia I.; Gomes, Ana M.; Malcata, F. Xavier; Freitas, Ana C.Inulin and fructooligosaccharides were studied for their prebiotic effect upon growth/survival of probiotic bacteria and technological potential in probiotic food processing, via characterization of glycolysis, proteolysis and lipolysis in curdled milk matrices; the ultimate goal is the manufacture of synbiotic cheeses. Prebiotic compounds did not significantly affect growth/viability of all strains studied, except Lactobacillus acidophilus La-5. Proteolysis indices revealed considerable casein degradation in probiotic and synbiotic matrices inoculated with Bifidobacterium lactis B94 and Lactobacillus casei-01; lower values were achieved in those inoculated with L. acidophilus La-5, yet a synbiotic effect was apparent in NPN values. Lipolysis was not extensive over storage, irrespective of matrix type; however, interesting differences in terms of the qualitative free fatty acids profile were observed. CLA isomers, and a-linolenic and g linolenic acids were detected upon 15 d of ripening of all inoculated matrices. Principal component analysis was able to discriminate the various matrices according to degree of maturation, throughout the ripening period. Microbiological and biochemical parameters unfolded a very good technological potential, especially of B. lactis B94 and L. casei-01, to produce novel types of functional dairy matrices e although extrapolation to actual cheeses should still be done with care, because e.g. syneresis was not considered.
- Edible films and coatings from whey proteins: a review on formulation, and on mechanical and bioactive propertiesPublication . Ramos, Óscar L.; Fernandes, João C.; Silva, Sara I.; Pintado, Manuela E.; Malcata, F. XavierThe latest decade has witnessed joint efforts by the packaging and the food industries to reduce the amount of residues and wastes associated with food consumption. The recent increase in environmental awareness has also contributed toward development of edible packaging materials. Viable edible films and coatings have been successfully produced from whey proteins; their ability to serve other functions, viz. carrier of antimicrobials, antioxidants, or other nutraceuticals, without significantly compromising the desirable primary barrier and mechanical properties as packaging films, will add value for eventual commercial applications. These points are tackled in this review, in a critical manner. The supply of whey protein-based films and coatings, formulated to specifically address end-user needs, is also considered.
- Modeling the kinetics of whey protein hydrolysis brought about by enzymes from Cynara cardunculusPublication . Barros, Rui M.; Malcata, F. XavierThe purpose of this research work was to study the proteolytic activity of aqueous crude extracts of flowers of the plant Cynara cardunculus on the major whey proteins, namely, â-lactoglobulin (â-Lg) and R-lactalbumin (R-La). These extracts, containing a mixture of cardosins A and B (i.e., two distinct aspartic proteases), have been employed for many years in traditional cheese-making in Portugal and Spain. Cow’s milk sweet whey was incubated for up to 24 h at various ratios of addition of crude enzyme extract, under controlled pH (5.2 and 6.0) and temperature (55 °C). The samples collected were assayed by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A mechanistic model was proposed for the kinetics of the hydrolysis process, which is basically a double-substrate, double-enzyme Michaelis-Menten rate expression; the kinetic parameters were estimated by multiresponse, nonlinear regression analysis. The best estimates obtained for the specificity ratio (i.e., kcat/Km) of each cardosin within the mixture toward each whey protein indicated that said aspartic proteases possess a higher catalytic efficiency for R-La (0.42- 4.2 mM-1âs-1) than for â-Lg (0-0.064 mM-1âs-1), at least under the experimental conditions used. These ratios are below those previously reported for caseins and a synthetic hexapeptide. Cardosins are more active at pH 5.2 than at pH 6.0 and (as expected) at higher enzyme-to-substrate ratios.