Immobilization of β-Glucosidase and Its Application for Enhancement of Aroma Precursors in Muscat Wine

Enzyme immobilization is becoming more widely practised in biotechnology because of the advantages that this method brings. In this study, commercial β-glucosidase for aroma released in winemaking was immobilized on diverse supports (alginate–chitin, chitosan–chitin) by using different methods. It was found that the most appropriate matrix was chitosan by adsorption and reticulation. The optimal immobilization conditions were pH 3.5, immobilization time 120 min, and concentration of cross-linker glutaraldehyde 0.25 %. Stability of the immobilized enzymes was assessed, which revealed a number of advantages, such as a lower enzyme dose required for immobilization (367 times lower than the free enzyme dose recommended by the manufacturer), high stability over time, and reusability. In vitro studies of cellobiose and in vivo studies of wine and aroma precursors isolated from grape must yielded similar outcomes with respect to enzyme hydrolysis of free and immobilized proteins.     

Using High-Pressure Processing for Reduction of Proteolysis and Prevention of Over-ripening of Raw Milk Cheese

High-pressure-processing (HPP) at 400 or 600 MPa was applied to cheeses made from ewe raw milk, on days 21 or 35 after manufacturing, to reduce proteolysis and prevent over-ripening. The characteristics of HPP and non-pressurized (control) cheeses were compared during ripening at 8 °C until day 60 and further storage at 4 °C until day 240. HPP and control cheeses showed similar pH values throughout ripening, but on day 240 pH values remained 0.4–0.6 units lower for HPP cheeses than for the control cheeses. Casein degradation was significantly retarded in the 600 MPa cheeses. Their α-casein concentration was 48–52 % higher on day 60 and 30–33 % higher on day 240 than in the control cheeses while β-casein concentration was 25–26 % higher on day 60 and 100–103 % higher on day 240. No significant differences in para-κ-casein concentration between cheeses were found on day 60, but on day 240, it was 22–35 % higher in the 600 MPa cheeses than in the control cheese. Hydrophilic peptides, hydrophobic peptides and total free amino acids evolved similarly in HPP and control cheeses during the 60-day ripening period. However, on day 240 hydrophilic peptides were at 34–39 % lower levels in the 600 MPa cheeses than in the control cheeses, hydrophobic peptides at 7–16 % lower levels and total free amino acids at 25–29 % lower levels. Flavour intensity scores increased at a slower rate in HPP cheeses than in the control cheese. Flavour quality declined markedly in the control cheeses during refrigerated storage while it did not vary significantly in 600 MPa cheeses.     

Evaluation of SPE as Preparative Technique for the Analysis of Phenolic Metabolites in Human Feces

Solid phase extraction (SPE) methodology has been evaluated as a cleanup strategy prior to the analysis of phenolic metabolites in fecal samples by UPLC–DAD–ESI–TQ MS. Among the sorbents tested, Oasis® HLB led to the higher phenolic standard recoveries. Sample acidification (0.4 M HCl, final concentration) before SPE considerably improved standard recoveries. Values of the process efficiency (C_SPE/C_{Without SPE}) for a standard solution containing gallic acid, protocatechuic acid, caffeic acid, benzoic acid, 3-phenylpropionic acid, (+)-catechin, (?)-epicatechin, procyanidin B2, and 4-hydroxybenzoic 2,3,5,6 d₄ acid were acceptable (>90 %) for all compounds, except for procyanidin B2 (26 %). The developed SPE methodology was applied to fecal samples of individuals subjected to a wine intervention study. Phenolic metabolites, including intermediate metabolites (phenyl-γ-valerolactones and phenylvaleric acid derivatives) and end products (simple phenols, hydroxyphenylpropionic, hydroxyphenylacetic, hydroxycinnamic, and hydroxybenzoic acids) were identified. Most of the compounds (n?=?14) exhibited values of process efficiency between 85 and 115 %. Although some compounds (n?=?4) showed process efficiency>115 %, there was a group of metabolites (4-O-methylgallic acid, syringic acid, and 4-hydroxy-5-(3′,4′-dihydroxyphenyl)-valeric acid) whose process efficiency was <85 %, which represented a serious limitation and made us to discard SPE as a preparative technique for the analysis of these phenolic metabolites. Finally, the paper reports the concentrations of phenolic metabolites in a randomized set of human fecal samples from healthy volunteers (n?=?15) without any previous SPE application. Large inter-individual variability was observed, which was attributed to differences in human gut microbiota composition.     

Sensory Characterization and Consumer Preference Mapping of Fresh Sausages Manufactured with Goat and Sheep Meat

The main objective of this study was the sensory characterization, by a taste and a consumers’ panel, of fresh sausages from 140 culled goats and 140 culled ewes. Species and type of preparation effects were studied. All data were previously analyzed by analysis of variance. Taste panel data were analyzed by a Generalized Procrustes Analysis (GPA). Consumers’ panel data were analyzed by Preference Mapping. The 1st 2 factors explained 88.22% of total variation in GPA. Different sausages samples were perfectly differentiated by assessors. Goat sausages have been considered harder, more fibrous, and less juicy than sheep sausages. The panelists observed that sheep sausages without paprika had greater intensity of flavor, tasted spicy, and had an off‐odor, while goat sausages with paprika were considered sweeter. Consumers’ panel did not show any preference for the different types of sausages. This means that all types of sausages can have market opportunity.     

Production of fermentable media from vine‐trimming wastes and bioconversion into lactic acid by Lactobacillus pentosus

Trimmings of vineshoots, an agricultural waste with little use, were hydrolysed with dilute sulphuric acid (1–5%) in order to obtain sugar solutions suitable as fermentation media. The operational conditions for hydrolysis were selected on the basis of both the generation of hemicellulosic sugars (mainly xylose) and glucose and the concentrations of reaction byproducts affecting fermentation (furfural, hydroxymethylfurfural and acetic acid). Hemicellulosic hydrolysates were supplemented with nutrients and fermented with Lactobacillus pentosus, without any previous detoxification stage, to produce lactic acid. Under the best operational conditions assayed (3% H₂SO₄ and 15 min), 21.8 g lactic acid l^?1 was produced (Q_P = 0.844 g l^?1 h^?1, Y_P/S = 0.77 g g^?1), which represents a theoretical yield of 99.6%. Acetic acid was the primary byproduct formed from xylose, at about 25% of the lactic acid level. Copyright © 2004 Society of Chemical Industry     

Development of a method for genetic identification of four species of anchovies: E. encrasicolus, E. anchoita, E. ringens and E. japonicus

Cytochrome b has been successfully employed for genetic identification of four species of anchovies (Engraulis spp) using two methodologies: PCR–RFLP and FINS. The first method allowed the identification of Engraulis anchoita, Engraulis ringens and Engraulis japonicus–Engraulis encrasicolus. In some cases, with a determined restriction profile, this technique was able to differentiate E. japonicus from E. encrasicolus. The second method allowed the identification of those four species and demonstrates that FINS is a suitable technique for the identification of all species studied in this work. Phylogenetic trees show that sequences of E. encrasicolus are grouped into two different clusters. These results are consistent with the previously published data which suggest that some species of genus Engraulis could be cryptic species, being one specie or population distributed in the oceanic habitat and the other one around the coast.     

Development of Quality Index Method (QIM) scheme for Acoupa weakfish (Cynoscion acoupa)

A Quality Index Method (QIM) scheme for gutted and iced Acoupa weakfish (Cynoscion acoupa) was developed and its efficiency for freshness evaluation was compared with instrumental colour analysis, microbial and chemical methods. The QIM scheme comprises sensory evaluation of 14 parameters, reaching a total sum of 23 demerit points. The evolution of Quality Index (QI) was identical in two independent storage experiments and could be represented by the equation QI = 1.3593 × days − 0.3822 (R² = 0.9614, P < 0.0001). The QIM results indicated a shelf life of 8–9 days, when the sensory quality was considered unacceptable. The storage time affected a∗ and b∗ values for fish gill and caudal fin, respectively. Psychrotrophic bacteria counts (PBC) increased at different rates during the iced storage of fish in three independent storage experiments, reaching the maximum recommended limit for marginally acceptable quality products of 10⁷ CFU/g between 6 and 14 days. The shelf life of Acoupa weakfish estimated by QIM was slightly longer than that evaluated by PBC. The rate and pattern of total volatile base nitrogen and trimethylamine production was different in fish from three independent storage experiments. The use of QIM scheme was a reliable way of assessing freshness of Acoupa weakfish.