No abstract

The use of these aromatic plants as natural covers on cheese can satisfactorily inhibit the growth of some mycotoxicogenic fungal spoilers. Among the volatile compounds present, α- and β-phellandrene were confirmed as the most relevant in the inhibition.

The study of active compound transference during cheese elaboration was achieved. The antimicrobial results in fortified cheeses with REO showed a preventive effect in the case of clostridial species, which are responsible for late cheese blowing.

World wine industry transforms 10% -25% of raw grapes into residues, mainly represented by lees, grape marcs, seeds and stems. These byproducts are a rich source of polyphenols and therefore they can be used to produce new added value products. The aim of this work was to determine the best process conditions (treatment time, % of ethanol and pH of the solvent) during solid-liquid extraction of polyphenols from grape marcs, by analyzing the phenolic content of the extracts, namely: total polyphenol content, flavanols, flavonols, phenolic acids and anthocyanins. Antioxidant activity of the extracts was also determined. An extraction time of two hours was enough since longer times did not increase process yields. Best extraction yields were obtained for 75% ethanol solutions. Basic pH led to better yields in extracting media with low percentage of ethanol, whereas acid pH presented better extraction yields in extracting media with high percentage of ethanol. Among all the polyphenols extracted, anthocyanins were the most abundant representing over 40% of the total. In general, the best process conditions were 2 h of extraction in a 75% EtOH liquid mixture at pH = 2.

During the last decades, essential oils (EOs) have been proven to be a natural alternative to additives or pasteurization for the prevention of microbial spoilage in several food matrices. In this work, we tested the antimicrobial activity of EOs from Melissa officinalis, Ocimum basilicum, and Thymus vulgaris against three different microorganisms: Escherichia coli, Clostridium tyrobutyricum, and Penicillium verrucosum. Pressed ewes’ cheese made from milk fortified with EOs (250 mg/kg) was used as a model. The carryover effect of each oil was studied by analyzing the volatile fraction of dairy samples along the cheese-making process using headspace stir bar sorptive extraction coupled to gas chromatography/mass spectrometry. Results showed that the EOs contained in T. vulgaris effectively reduced the counts of C. tyrobutyricum and inhibited completely the growth of P. verrucosum without affecting the natural flora present in the cheese. By contrast, the inhibitory effect of M. officinalis against lactic acid bacteria starter cultures rendered this oil unsuitable for this matrix.

Given their broad spectrum, cephalosporins are used for combating mastitis in dairy species. Many cephalosporins, such as cephalexin, have not been authorized for use in lactating sheep and because veterinary drugs for use in small species are lacking, the regulations of several countries allow extra-label use. Incorrect use of extra-label tools may cause residues in milk, and could negatively affect public health by provoking technological failures in the dairy fermenting processes. The effects of cephalexin, at concentrations close to its European Maximal Residue Limit (MRL), have been studied in set-type yogurts made from sheep's milk. Milk was fortified at different cephalexin concentrations and stored yogurts were evaluated in acidification, textural parameters and microbial evolution terms. The results showed that cephalexin concentrations equal to or below its MRL could mainly inhibit normal Streptococcus thermophilus growth and provoke some alterations to acidity parameters, which were more marked in the L(+)-lactic acid isomer.Keywords: yogurt; sheep milk; cephalosporin antibiotics; antimicrobial agents; lactic acid; acidity; viscosity; texture; microorganisms Dado su amplio espectro, las cefalosporinas se utilizan con frecuencia para tratar mastitis en especies lecheras. Muchas cefalosporinas, como la cefalexina, no están autorizadas para su uso en ovejas en lactación, pero debido a la escasez de medicamentos autorizados para su uso en especies menores como ésta, la legislación de muchos países permite su uso "extra label" (fuera de etiquetado). La utilización incorrecta de la herramienta "extra-label" podría causar residuos en leche, afectar negativamente a la salud pública y provocar fachos tecnológicos en los procesos fermentativos lácteos. En este trabajo se ha estudiado el efecto que concentraciones cercanas al Límite Máximo de Residuos europeo (LMR) podría tener sobre yogures elaborados con leche de oveja. Para ello, se han adicionado diferentes concentraciones de cefalexina a leche y los yogures elaborados con ésta se han evaluado a lo largo de su almacenamiento sus parámetros de acidificación, textura y evolución microbiana. Los resultados demostraron que concentraciones de cefalexina iguales o inferiores al LMR inhibieron el normal desarrollo de Streptococcus thermophilus, y causaron algunas alteraciones en los parámetros de acidez, principalmente en sobre el isómero L(+) del ácido láctico.

This study aimed to inhibit the growth of Escherichia coli and Clostridium tyrobutyricum, common bacteria responsible for early and late cheese blowing defects respectively, by using novel aqueous extracts obtained by dynamic solid-liquid extraction and essential oils obtained by solvent free microwave extraction from 12 aromatic plants. In terms of antibacterial activity, a total of 13 extracts inhibited one of the two bacteria, and only two essential oils, Lavandula angustifolia Mill. and Lavandula hybrida, inhibited both. Four aqueous extracts were capable of inhibiting C. tyrobutyricum, but none were effective against E. coli. After extracts' chemical composition identification, relationship between the identified compounds and their antibacterial activity were performed by partial least square regression models revealing that compounds such as 1,8 cineole, linalool, linalyl acetate, β-phellandrene or verbene (present in essential oils), pinocarvone, pinocamphone or coumaric acid derivate (in aqueous extracts) were compounds highly correlated to the antibacterial activity.

Growth of undesirable moulds is one of the major causes of defects in modern cheese production, and it is necessary to discover natural antifungal substances that are non-toxic to humans. Saffron spice has been successfully used as a new ingredient in some Italian or Spanish cheeses, but transference of safranal (the main compound responsible for saffron aroma) during cheesemaking has not yet been studied. In this study, the distribution of safranal in cheese, whey and requesón (Spanish whey cheese) and the antifungal potential of whey fractions against the mould Penicillium verrucosum were studied. To this end, a duplicate fabrication of cheeses was performed with raw ewe's milk with the addition of 40 μg safranal.kg −1 or control milk (no safranal addition). Safranal was more concentrated in cheese and requesón (78.91 and 76.95 μg.kg −1 , respectively) than in whey and requesón whey (35.19 and 34.64 μg.kg −1 , respectively). These liquid fractions showed good antifungal properties and inhibited mould with a safranal concentration of around 35 μg.kg −1 , while a solution of 80 μg.kg −1 was required for a standard safranal solution to obtain a similar inhibition. These results reveal that whey has a synergistic effect with safranal in preventing cheese spoilage by moulds, which encourages making full use of this problematic by-product.