José Manuel Rodríguez-Nogales

Estimation of the percentage of transgenic Bt maize in maize flour mixtures using perfusion and monolithic reversed-phase high-performance liquid chromatography and chemometric tools

The estimation of the percentage of transgenic Bt maize in maize flour mixtures has been achieved in this work by high-performance liquid chromatography using perfusion and monolithic columns and chemometric analysis. Principal component analysis allowed a preliminary study of the data structure. Then, linear discriminant analysis was used to develop decision rules to classify samples in the established categories (percentages of transgenic Bt maize). Finally, linear regression (LR) and multivariate regression models (namely, principal component analysis regression (PCR), partial least squares regression (PLS-1), and multiple linear regression (MLR)) were assayed for the prediction of the percentages of transgenic Bt maize present in a maize flour mixture. Using the relative areas of the protein peaks, MLR provided the best models and was able to predict the percentage of transgenic Bt maize in flour mixtures with an error of ±5.3%, ±2.3%, and ±3.8% in the predictions of Aristis Bt, DKC6575, and PR33P67, respectively.

Immobilization of Oenococcus oeni in lentikats® to develop malolactic fermentation in wines

Entrapment of Oenococcus oeni into a polymeric matrix based on polyvinyl alcohol (PVA) (Lentikats®) was successfully used to get a better development of malolactic fermentation (MLF) in wine. The incubation of immobilized cells in a nutrient medium before starting the MLF, did not improve the degradation of malic acid. In only one day, 100% of conversion of malic acid was achieved using a high concentration of immobilized cells (0.35 g gel/ml of wine with a cell‐loading of 0.25 mg cells/mg of gel). While a low concentration of 0.21 g gel/ml of wine (cell‐loading of 0.25 mg cells/mg of gel) needed 3 days to get a reduction of 40%. The entrapped cells could be reused through six cycles (runs of 3 days), retaining 75% of efficacy for the conversion of malic acid into lactic acid. The immobilized cells in PVA hydrogels gave better performance than free cells because of the increase of the alcohol toleration. Consequently, the inhibitory effect of ethanol for developing MLF could be reduced using immobilized cells into PVA hydrogels.

Antioxidant Properties of Sparkling Wines Produced with β-Glucanases and Commercial Yeast Preparations

UNLABELLED The aim of this study was to evaluate the in vitro antioxidant potential of sparkling wines produced with β-glucanases, autolysated yeasts, yeast cell walls, and purified mannoproteins. Total antioxidant capacity (measured by 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical-scavenging method and ferric reducing antioxidant power [FRAP] assay), and hydroxyl radical-scavenging activity (HRSA) were higher in the wine samples with coadjuvants (in relation to the control wine). The highest values of antioxidant activity were achieved with purified mannoproteins and, in lesser extent, with β-glucanases. Neutral polysaccharides and total proteins were highly and positively correlated with DPPH, FRAP, and HRSA assays. However, correlations between the levels of each different phenolic family and antioxidant and radical-scavenging activities were not found. β-Glucanase and commercial yeast preparations can be excellent coadjuvants to increase the antioxidant properties of sparkling wines. PRACTICAL APPLICATION β-Glucanase and commercial yeast preparations can be excellent coadjuvants to increase the antioxidant properties of sparkling wines. The suggested improvement has significant implication for the production of high added value sparkling wines.

Effect of somatic cell counts on ewes' milk protein profile and cheese-making properties in different sheep breeds reared in Spain

Bulk tank ewes milks from Assaf, Castellana and Churra breeds categorized within three different Somatic Cell Count (SCC) groups (LSCC: <500,000; MSCC: 1,000,000 to 1,500,000; and HSCC: 2,500,000 to 3,000,000 cells ml-1) were used to investigate changes in capillary electrophoresis protein profiles and cheese-making properties. The results do not reveal a significant effect of SCC on total casein contents, because the sum of beta-caseins decreased as SCC increased; no statistically significant differences were observed for the sum of alpha-caseins, and the values of kappa-casein were higher in the HSCC milk. However, the soluble proteins other than alpha-lactalbumin and beta-lactoglobulin increased with SCC. Regarding the effect of breed, the Assaf breed had the lowest contents of kappa-CN, alpha s1-I-CN, alpha s1-II-CN 1-CN, alpha s1-III-CN, beta1-CN and beta2-CN. The protein profile was significantly correlated with curd textural properties. alpha s1-I-CN was the most influential variant because it was positively correlated with a large number of textural parameters. Cheese yield was positively correlated with all casein variants except alpha s1-III-CN, showing that the milk from local breeds were more suitable for cheese-making due to their higher contents of all the casein variants. Regarding curd texture properties LSCC milk curds showed more cohesiveness, associated with its lower content of alpha s1-III-CN and Castellana milk curds showed the highest values for firmness owing to their higher content of alpha s1-I-CN.

Research progress in coating techniques of alginate gel polymer for cell encapsulation

Cell encapsulation is used as a biotechnology tool to solve the technological problems derived from handling and application of cells in a great range of fields. This involves immobilization of the cells within a polymeric gel that permits the preservation of their metabolic activity. Alginate is widely established as the most suitable polymer for cell encapsulation. However, alginate gel capsules suffer several disadvantages because of their lack of mechanical and chemical stability. This review summarizes results of recent advances in coating techniques that include ionic and covalent cross-linking between alginate and coating materials for cell encapsulation as a strategy to solve the disadvantages mentioned before. Throughout this review, physicochemical properties of coated-alginate capsules and the effect of coating process on metabolic activity and viability of immobilized cells have been specially discussed.

Highly Efficient Malolactic Fermentation of Red Wine Using Encapsulated Bacteria in a Robust Biocomposite of Silica-Alginate

Bacteria encapsulation to develop malolactic fermentation emerges as a biotechnological strategy that provides significant advantages over the use of free cells. Two encapsulation methods have been proposed embedding Oenococcus oeni, (i) interpenetrated polymer networks of silica and Ca-alginate and (ii) Ca-alginate capsules coated with hydrolyzed 3-aminopropyltriethoxysilane (hAPTES). On the basis of our results, only the first method was suitable for bacteria encapsulation. The optimized silica-alginate capsules exhibited a negligible bacteria release and an increase of 328% and 65% in L-malic acid consumption and mechanical robustness, respectively, compared to untreated alginate capsules. Moreover, studies of capsule stability at different pH and ethanol concentrations in water solutions and in wine indicated a better behavior of silica-alginate capsules than untreated ones. The inclusion of silicates and colloidal silica in alginate capsules containing O. oeni improved markedly their capacity to deplete the levels of L-malic acid in red wines and their mechanical robustness and stability.

Testing SensoGraph, a geometric approach for fast sensory evaluation

Abstract This paper introduces SensoGraph, a novel approach for fast sensory evaluation using two-dimensional geometric techniques. In the tasting sessions, the assessors follow their own criteria to place samples on a tablecloth, according to the similarity between samples. In order to analyse the data collected, first a geometric clustering is performed to each tablecloth, extracting connections between the samples. Then, these connections are used to construct a global similarity matrix. Finally, a graph drawing algorithm is used to obtain a 2D consensus graphic, which reflects the global opinion of the panel by (1) positioning closer those samples that have been globally perceived as similar and (2) showing the strength of the connections between samples. The proposal is validated by performing four tasting sessions, with three types of panels tasting different wines, and by developing a new software to implement the proposed techniques. The results obtained show that the graphics provide similar positionings of the samples as the consensus maps obtained by multiple factor analysis (MFA), further providing extra information about connections between samples, not present in any previous method. The main conclusion is that the use of geometric techniques provides information complementary to MFA, and of a different type. Finally, the method proposed is computationally able to manage a significantly larger number of assessors than MFA, which can be useful for the comparison of pictures by a huge number of consumers, via the Internet.

Effect of stressful malolactic fermentation conditions on the operational and chemical stability of silica-alginate encapsulated Oenococcus oeni

Oenococcus oeni was encapsulated into inter-penetrated polymer networks of silica-alginate (SiO2-ALG). Fourier transform infrared spectroscopy analysis proved the presence and the polycondensation of the siliceous material used in SiO2-ALG capsules. Environmental scanning electron microscopy showed that the structure of SiO2-ALG biocapsules was rougher than in alginate (ALG) biocapsules. The behaviour of SiO2-ALG biocapsules was evaluated at pH 3.0-3.6 and alcohol degrees of 12-15%. Repeated-batch malolactic fermentations (MLF) demonstrated that SiO2-ALG biocapsules can be reused efficiently for five times in either low-pH or high-ethanol wines, while free bacteria only can be used once under the most favourable MLF conditions. The inclusion of siliceous materials into ALG hydrogel improved the stability of the biocapsules, reducing their shrinking and achieving an excellent integrity under winemaking conditions. These results proved the possibility of industrial application of SiO2-ALG biocapsules in winemaking.