查看更多>>摘要：Using Torulaspora delbrueckii as starter culture for alcoholic fermentation (AF) is a current trend for enhancing the quality of red wines. As red winemaking usually requires subsequent malolactic fermentation (MLF), the compatibility of this yeast and Oenococcus oeni is a key factor for a successful fermentative process. In this work we study the interactions of T. delbrueckii and O. oeni in wines from grapes with different degrees of maturity. The results showed higher total polyphenolic index (TPI) values in T. delbrueckii wines. Moreover, the aromatic characteristics were improved in these wines, compared to the wines inoculated only with Saccharomyces cerevisiae. There was also a reduction in some inhibitor compounds for O. oeni, for instance medium chain fatty acids, as a result of the fermentation with this non-Saccharomyces. Overall, the use of T. delbrueckii resulted in better MLF performances.
查看更多>>摘要：Essential oils have been studied to replace synthetic chemical preservatives, among these oils, the thyme essential oil stands out. However, in addition to promoting microbial control, synthetic chemical preservatives impart a characteristic color to inlaid products, a parameter not attained by the application of essential oils. This study aimed to evaluate the effect of the joint addition of thyme essential oil and powdered beet juice to meat sausage, for a partial or total reduction of the addition of nitrates and nitrites. The thyme essential oil showed a high inhibitory action against Staphylococcus aureus and Escherichia coli in the concentration of 9.17 mg/mL, and bactericidal effect in the concentrations of 9.17 mg/mL and 36.68 mg/mL respectively, in all tests applied in vitro. When applied to meat sausages, it showed an inhibitory effect against coagulase-positive Staphylococcus, reducing the microorganism count, and partial inhibition of aerobic mesophilic bacteria. No interference was observed in the multiplication of thermotolerant coliforms in the meat product. When evaluated sensorially, the sausage presented good general acceptability, with acceptance levels above 75%. The combined uses of thyme essential oil and powdered beet juice showed potential viability for use in substitution for nitrates and nitrites in meat sausages.
查看更多>>摘要：Low molecular weight (MW) fucoidans have been proved with excellent tyrosinase inhibitory activity, which may proposed as a potential anti-browning ingredient for fruit and vegetable fresh-keeping agent. This study was conducted to obtain a low MW fucoidan fraction with high tyrosinase inhibitory capacity from Laminaria japonica crude fucoidan by fucoidanase degradation and to preliminary explore its type of tyrosinase inhibition and the application in browning inhibition of fresh-cut fruit. Firstly, the wild fucoidan-degrading strain, Flavobacteriaceae RC2-3, was mutated by UV irradiation and the fucoidanase production was improved by 40.5%. Fucoidan, which degraded by purified fucoidanase for 2 h, presented favourable tyrosinase inhibitory ability and were then separated by ultrafiltration. The fucoidan fraction with MW below 5 kDa (FF5) demonstrated the best tyrosinase inhibitory effect and shown obvious browning inhibition of fresh-cut apple slices. The inhibitory kinetics revealed that FF5 was a quite effectively competitive inhibitor of tyrosinase. The results of this study suggested that FF5 could be used as a promising browning inhibitor in the preservation of fruits and vegetables.
查看更多>>摘要：Polyphenols are the key taste and health components of tea. Typically, chemical analysis is used to determine the total polyphenol (TP) content of tea. However, this process is time consuming. In this study, the TP content of six tea types, namely green, white, yellow, oolong, black, and dark, was assessed using near-infrared hyperspectral imaging. Here, 100% accuracy was achieved for both the calibration and prediction sets for qualitative discrimination of tea by using the principal component analysis-K-nearest neighbor model. Important wavelengths of TP were selected using the regression coefficients (RCs) of the partial least squares regression (PLSR) model. The proposed RC-PLSR model yielded satisfactory prediction results with a residual predictive deviation of 3.34. The differences in the spatial distribution of TP in various tea samples were visualized using distribution maps. This study provided a rapid and nondestructive method for the identification of tea types and the visualization of the TP content of tea.
查看更多>>摘要：This study aimed to evaluate the effect of five substitution levels (0%; 15%; 30%; 45%, and 60%) of sodium chloride (NaCl) by potassium chloride (KCl) on the physical, chemical, technological, bacteriological and sensory qualities of cooked "spam-like" products formulated with mechanically separated tilapia meat (MTM). Substitution of NaCl by KCl increased the weight loss during cooking (between 6.65 and 17.55 g/100 g), fat exudation (between 0.64 and 2.91 g/100 g) and water exudation (between 3.32 and 5.91 g/100 g), and decreased hardness, springiness, cohesiveness and chewiness of the cooked "spam-like" products, representing evidence of the fundamental action of NaCl in the dissolution of myofibril proteins. All the samples were adequate for consumption considering their bacteriological aspects, and the treatments from 15% to 45% substitution showed greater sensory acceptance. The reduction of sodium between 1.05 and 9.2% by substituting NaCl with KCl made it possible to produce a "spam-like" product from MTM, allowing for exploiting this by-product. The product made with 15% substitution of NaCl by KCl was considered the best treatment concerning the technological characteristics, showing less fat and water exudation, less lipid oxidation and higher scores for sensory flavor and global impression.
查看更多>>摘要：In most bacteria, Glutamate decarboxylase (GAD) activity significantly reduces at pH > 6. Since L-glutamate is neutral to slightly alkaline, a large amount of hydrochloric acid must be added to the reaction mixture. Acidic reaction conditions greatly increase the corrosion of production equipment and shorten the life of manufacturing equipment. Therefore, this study aims at studying the overexpression of recombinant GAD that is active at the neutral pH and high-level production of gamma-aminobutyric acid. A gene sequence encoding GAD of Enterococcus faecium DO was cloned into PET21a (+) and was overexpressed in Escherichia coli BL21 (DE3). The construct was confirmed by colony PCR and double digested with BamHI and XhoI. The result from Western blot analysis showed a signal band at the molecular mass of 54 kDa. The specific activity of the recombinant GAD was 78.17 U mg(-1) at 45 degrees C and pH = 6.6. It was reduced rapidly when pH > 7.8. The Km, Vmax, and kcat values of recombinant GAD were 1.8 mM, 12.9 mu mol L-1 min-1, and 0.43 s(-1), respectively. Therefore, recombinant GAD is a potent candidate for GABA production in food and pharmaceutical industries, because it increases the efficiency of GABA synthesis, especially in foods with a neutral pH range.
查看更多>>摘要：The present work applied the ultrasound pretreatment (UPT) to reduce oil absorption and improve quality features (texture) of potato chips. The oil content, oil fractions, cell viability, cell morphology, oil distribution, color changes, and texture of potato chips were discussed. UPT (360 W, 60 min) significantly decreased penetrated surface oil content of potato chips, causing the 27.66% decrease in total oil content. The changes in cell viability induced by ultrasound resulted in variations of oil distribution at a macro level. Higher ultrasound power destroyed more cells on the edge, which further resulting in more oil absorption on the edge of potato chips. Disrupting cell structure changed oil distribution at a micro level. When the ultrasound power was increased to 600 W, the oil showed more uneven distribution because of the destroyed cellular structure. Texture testing pointed out that UPT decreased the hardness of potato chips.
查看更多>>摘要：Olive leaf extract (OLE), as a natural antioxidant, was encapsulated within nanostructured lipid carrier (OLE-NLC) and the physico-chemical, microstructure, physical stability, antioxidant activity, and encapsulation efficiency (EE%) were evaluated. Then, it was loaded into the pectin-sodium caseinate hydrogel network and its antioxidant and physicochemical properties were examined during storage. The particle size, polydispersity index (PDI), and zeta-potential (lambda) of the OLE-NLC nanoparticles and OLE-NLC containing hydrogel were 112.9 and 303 nm, similar to 0.34 and 0.58, respectively. Spherical particles with flat surface were observed by scanning electron microscopy (SEM) for both systems. During 40 days of storage at 4 degrees C, the NLC particle size was stable and remained <100 nm. The Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed that OLE was loaded physically in both systems considering the formation of new hydrogen bonds and amorphous structure of both systems. Rheological studies showed the Newtonian behavior of the hydrogel (dilute The retention of antioxidant activity was higher in OLE-NLC containing hydrogel for 30 days. Overall, OLE-NLC containing hydrogel could be suitable for OLE encapsulation to maintain its antioxidant properties against environmental factors and also could be considered in high-fat foods to reduce oxidation and enhance their nutritional properties.
查看更多>>摘要：Ohmic heating (OH) encompasses interesting benefits towards thermal processing. Envisaging an increasing relevance of soybean protein as an alternative non-animal protein, it is important to understand how OH can contribute to the quality and immunoreactivity of soybean-derived products. This study describes, for the first time, the impact of OH when applied at different electrical frequencies (50 Hz-20 kHz) and moderate electric field intensities (up to 20 V/cm), on the leakage of metals from the electrodes and immunoreactivity aspects of soybean protein isolate (SPI). This was achieved by monitoring the occurrence of electrochemical reactions and evaluating IgG-binding capacity. OH performed at 50 Hz and 95 degrees C induced significant alterations on the intrinsic fluorescence of SPI (p <= 0.05) and the release of detectable amounts of Fe/Ni, with a subsequent reduction of 36% in the immunoreactivity of Gly m TI. The occurrence of non-thermal effects, as well as the interaction between protein and trace metals, may result in a partial blockage of protein epitopes, thus impairing specific antibody binding. These findings present novel information about the importance of OH parameters, such as electrical frequency and occurrence of electrochemical reactions, which can affect the structure and immunoreactivity of SPI fractions.
查看更多>>摘要：High-gravity brewing (HGB) is a common practise in industrial breweries. The aim of this study was to examine the effect of HGB on analytical and quality parameters of all-malt beer. Parameters were evaluated in bottomfermented (BF) beer and some data were compared with results from top-fermented (TF) beer. In both, BF and TF beer, two brews were produced where a higher original gravity (OG) beer was diluted to the level of a lower OG beer. Increased ester production was the principal reason for changes in the flavour profile. Especially higher levels of acetate esters (ethyl acetate, isoamyl acetate) affected beer aroma, creating fruity and solventlike odours. Higher alcohol and acetaldehyde contents were not affected by HGB. The use of HGB for BF beer did not affect important quality parameters such as thiobarbituric acid number (TBA) or foam stability. The content of beer ageing markers (carbonyl compounds) was also not affected by the use of the HGB technology. In sensorial evaluation, differences in flavours of BF HGB beer were evaluated in a triangle test. Beer without dilution was preferred by tasters, commenting on better harmony in bitterness and beer body.
NSTL
Elsevier