Peixoto, MartaFreitas, Ana SofiaCunha, AnaOliveira, Rui...
7页
查看更多>>摘要：Propolis is a complex mixture of resinous and balsamic material collected by bees from various plant sources which is then processed by salivary enzymes and mixed with other substances like beeswax. This natural product has several biological activities that may provide a wide range of applications. However, propolis low productivity and high diversity hamper its full and efficient use. In order to increase propolis availability and contribute to its standardization, essential for the manufacture of marketable products, blends of propolis were prepared with ethanol extracts of samples harvested from a Portuguese apiary over 2011 to 2015. These mixtures were chemically characterized in terms of total polyphenols and flavonoids, and tested for antioxidant potential and antimicrobial properties. The mixtures of propolis ethanol extracts generally show similar or better bioactivities than individual extracts, possibly due to synergisms between bioactive compounds. Our results suggest that blends of propolis samples from different years can retain or even potentiate the bioactivities of individual samples, namely antioxidant and antimicrobial activities. Therefore, blending could be a possible way of making a better and more efficient use of propolis and simultaneously contribute to its normalization, allowing large scale applications and adding more value to this remarkable natural product.
查看更多>>摘要：Experimental design methodology (mixture design) coupled to microdilution assay were used to study the potential interactions between several active compounds from three Moroccan essential oils (EOs) (M. pulegium, O. mixta and M. piperita) against S. aureus E. coli and C. tropicalis, to increase their sensitivity and to predict optimal formulations. EOs extraction was firstly obtained by hydrodistillation, then, their chemical composition was determined by GC/MS and their antimicrobial activity was evaluated. The optimization of antimicrobial activity of essential oils mixtures by augmented simplex-centroid design allowed us to model and validate statistically as well as to establish a prediction profile of the studied phenomena. The optimization of mixtures antimicrobial activities has highlighted the synergistic effect between M. piperita and M. pulegium essential oils. The optimal mixture predicted against E. coli, S. aureus and C. tropicalis corresponded to 54%/46%; 56%/44% and 55%/45% of M. piperita and M. pulegium essential oils, respectively. This study shows that the combination of essential oils may be applicable in the fight against emerging microbial drug resistance or useful as natural food preservatives.
查看更多>>摘要：Thermal and dry salt-curing processing are traditional methods for processing Prunus mume fruits (PMF) into food or medicine. This study aimed to investigate the composition of free and bound phenolics in PMF, and effects of thermal and dry salt-curing processing on phenolic profiles, antioxidant activity and bioaccessibility. Nineteen (free and bound) phenolic compounds were identified and quantified in raw PMF. Salt-curing caused a significant decrease in free and bound phenolic content, whereas no significant change was observed after thermal treatment. The concentration and distribution of individual phenolic compounds instead of composition in PMF were changed by thermal and salt-curing processing. The two processing methods differently decreased DPPH and ABTS antioxidant activity. The total phenolic bioaccessibility increased by 34.09% after thermal processing, while decreased by 87.92% after salt-curing. These results may indicate that thermal rather than salt curing is more preferably method for processing PMF to developing health foods and nutraceuticals.
查看更多>>摘要：Wheat gluten hydrolysates (WGH) and KCl were used to examine their effects on fermentation performances and physiological characteristics of brewer's yeast during very high gravity (VHG) fermentation. Results showed that all supplementations exhibited a notable promotion in yeast growth, glucose utilization, ethanol production, and physiological characteristics. Combination supplementation of 0.3% WGH and 0.5% KCl showed the best promotion effect with 6.38%, 9.41% and 8.68% of increases in biomass, glucose utilization and ethanol production, respectively. Moreover, combination addition of WGH and KCl also enhanced significantly membrane integrity and mitochondrial functionality of brewer's yeast. Amino acid compositions of WGH and intracellular metabolites analysis indicated that active nitrogen metabolism and high levels of stress resistant substances might be responsible for the improvement of growth and fermentation performances in brewer's yeast by nutrient supplementation.
查看更多>>摘要：Pixian doubanjiang (PXDB) is a famous fermentation condiment in China and throughout the world. However, detailed information regarding its metabolic mechanism remains scarce. This paper presents a comprehensive chemical profiling of PXDB during fermentation, to obtain a global understanding of the metabolite variations based on the untargeted metabolomics approach through ultra-performance liquid chromatography coupled with quadruple-time-of flight mass spectrometry (UHPLC-Q-TOF). Ninety-nine metabolites, including amino acids, small peptides, organic acids, fatty acids and phospholipids were proposed as key chemical markers for the first time. Meanwhile, the pathways' analysis revealed that the transformation of these metabolites was primarily associated with arginine biosynthesis, alanine, aspartic acid and glutamate metabolism, glycerol phospholipid metabolism, unsaturated fatty acid biosynthesis and citric acid cycle pathways. The comprehensive analysis of the metabolite changes is expected to help us explore the formation of the taste and flavor components in PXDB production.
Kyere, Emmanuel O.Popovich, David G.Palmer, JonWargent, Jason J....
7页
查看更多>>摘要：Mild stress of leafy greens by UV-C radiation has been reported to stimulate plant defences capable of reducing pathogens on produce surfaces. In this study, the attachment, survival and growth of Listeria monocytogenes was investigated on lettuces stressed with mild UV-C radiation (1.3 and 2.6 kJm- 2). Attachment of L. monocytogenes to UV-C stressed (1.3 kJm- 2) lettuce leaves after 1 h was significantly (p < 0.05) reduced by 1.4-1.5 log cfu/cm2. UV-C stress also reduced the survival of L. monocytogenes on lettuce by 1.8-1.9 log cfu/g 96 h after inoculation, however a higher dosage of UV-C stress (2.6 kJm- 2) did not inhibit the survival of L. monocytogenes. The total phenolic compounds in lettuce significantly increased following UV-C stress (1.3 kJm- 2) indicating the accumulation of polyphenols might have contributed to the inhibition of L. monocytogenes attachment and growth. Appropriate dosage of mild UV-C stress of lettuce can reduce the attachment, survival and growth of L. monocytogenes in lettuce and can therefore be explored further for application in fresh produce safety.
查看更多>>摘要：The effect of coffee bean quality (specialty and regular) and brewing method (cold and hot) on the sensory profile and physicochemical characteristics of coffee beverages was studied. Cold brew was prepared by immersion and hot brew coffee by French Press. Total dissolved solids (TDS), titratable acidity (TA), caffeine, trigonelline, 4 and 5- caffeoylquinic acids were quantified by instrumental methods, volatile compounds by GC-MS, and the coffee flavor was through quantitative sensory evaluation. Coffee beverages were more differentiated by brewing method than by the coffee bean quality used in the preparation. Cold brew coffees were mainly associated with volatile 2-methyl-butanal, 5-methyl furfural, and dihydro-2-methyl- 3 (2H) -furanone. Hot brew coffee beverages were identified with some specific furans and 2-methoxy-4-vinylphenol. No significant differences were found in TDS, caffeine, trigonelline, 4 and 5 caffeoylquinic acids. A higher TA was observed in hot coffee beverages than in cold brew coffees. Regular bean quality promoted undesirable sensory attributes in both cold and hot brew beverages. However, these attributes were perceived in higher intensity in hot brew coffee beverages. Thus, differences in brewing methods affect the extraction of the chemical compounds present in different coffee bean quality, translating into variations in the sensory profile.
查看更多>>摘要：Pastiness is a dry-cured ham defect that can be determined by sensory and chemical analysis. Since pastiness produces an increase of saliva viscosity, rheology might be useful to instrumentally evaluate this defect. The aim of this study was to evaluate the rheological behaviour of water extracts obtained in vitro mimicking the mastication of dry-cured ham samples with different pastiness intensities. Commercial samples from different groups (non-pastiness (NPG), medium pastiness (MPG) and high pastiness (HPG) groups) were sensorially and rheologically analysed. Effect of temperatures and HPP treatments at 7 degrees C, 20 degrees C and 35 degrees C were also evaluated. Results showed that apparent viscosity of the water extracts increased with the increase of pastiness and decreased with temperature. Significant differences (p < 0.05) were observed between NPG/MPG and HPG samples and between 25 degrees C and 37 degrees C in HPG. After HPP, sensory pastiness disappeared in samples from MPG at any temperature and decreased from 6.8 to 0.2 in samples from HPG only when HPP35 was used. Although the increase on viscosity of oral fluid is related to the sensory pastiness, other factors seem to be involved in the mechanism of pastiness perception. Despite this, HPG samples can be distinguished from MPG and NPG samples.
Chen, XiaoWang, JiayiStevenson, Ralph JamesAng, Xun...
9页
查看更多>>摘要：The rancid and tart off-flavor of goat milk limits the popularization of its associated products. In this study, a two-step enzymatic catalysis method was proposed to generate new aromatic notes that could alter the negative flavor perception of goat milk products. The goat milk fat was first hydrolyzed to prepare fatty acids (FFAs) as substrates, and then esterification was carried out for the synthesis of esters with pleasant notes. In the first step, the FFAs were sufficiently released, accounting for 97.5% of the volatile fraction. In the final reconstituted goat milk product, esters with sweet, floral, and fruity-like notes occupied more than 65% of the total volatile compounds, while the abundance of fatty acids characterized by unpleasant odor decreased by 75%. Especially, 4-methyloctanoic acid, one of the FFAs responsible for the "goaty" flavor, was not detected under the substrate molar ratio of 0.4. Moreover, the performance of four commercial lipases was investigated and compared during the first step. Lipozyme TL IM was the most efficient in the catalysis of lipid hydrolysis at 60 degrees C and pH 8.0. The two-step lipase-catalyzed product provided a sweet and fruity note to goat milk products and reduced the in-tensity of the unpleasant "goaty" flavor.
Garcia-Valle, Daniel E.Bello-Perez, Luis A.Agama-Acevedo, EdithAlvarez-Ramirez, Jose...
9页
查看更多>>摘要：Chickpea flour contains large fractions of protein and dietary fiber, which offer benefits for human health. This work studied the characteristics and in vitro starch digestibility of pastas with blends of semolina and chickpea flour. Texture analysis showed that chickpea flour induced significant reductions in hardness and elasticity of cooked pasta. The addition of the chickpea increased protein solubility (150-200%). The accessible thiols showed a marked increase, indicating that the formation of a protein network relied on sulfhydryl crosslinking between proteins and other pasta components. FTIR analysis showed that the above characteristics may be linked to the secondary structure of proteins since chickpea tend to form structures with a high content of beta-sheet configurations. The main advantage of using chickpea is in the in vitro digestibility since the effective starch content decreased from 74.67 +/- 0.95 g/100 g for semolina pasta to 41.25 +/- 1.17 g/100 g for chickpea pasta. The rapidly and slowly digestible starch fractions exhibited notable reductions of up 45%, which was attributed to the formation of complexes and to protective physical barriers of proteins on the starch granule. Non-conventional flours offer certain benefits for pasta formulations, but also certain challenges to stabilizing the pasta structure.
NSTL
Elsevier