Synthetic dyes are by far the most widely applied colourants in industry. However, environmental and sustainability considerations have led to an increasing efforts to substitute them with safer and ...more sustainable equivalents. One promising class of alternatives is the natural quinones; these are class of cyclic organic compounds characterized by a saturated (C6) ring that contains two oxygen atoms that are bonded to carbonyls and have sufficient conjugation to show color. Therefore, this study looks at the potential of isolating and applying quinone dye molecules from a sustainable source as a possible replacement for synthetic dyes. It presents an in-depth description of the three main classes of quinoid compounds in terms of their structure, occurrence biogenesis and toxicology. Extraction and purification strategies, as well as analytical methods, are then discussed. Finally, current dyeing applications are summarised. The literature review shows that natural quinone dye compounds are ubiquitous, albeit in moderate quantities, but all have a possibility of enhanced production. They also display better dyeability, stability, brightness and fastness compared to other alternative natural dyes, such as anthocyanins and carotenoids. Furthermore, they are safer for the environment than are many synthetic counterparts. Their extraction, purification and analysis are simple and fast, making them potential substitutes for their synthetic equivalents.
Graphic Abstract
Considering the growing interest in enzyme-based extraction technology as a safe and eco-friendly extraction technique, along with the relatively high cost associated with enzymatic applications, it ...became necessary to explore novel strategies aimed to improve enzyme activity. In this study, the impact of ultrasonic treatment on commercial cellulase and pectinase was investigated. As this effect may be influenced by various ultrasonic and enzyme-related parameters, changes in enzyme conformation were explored under optimal and non-optimal enzyme conditions. The intrinsic fluorescence spectrum was utilized as a tool for monitoring these changes. Additionally, the enzyme's catalytic potential was also assessed under the same conditions. Results indicated that the impact of ultrasonic treatment on enzyme conformation primarily depends on the total ultrasonic energy delivered to the system, rather than other ultrasonic parameters such as power, sample volume, treatment time, or duty cycle. The maximum relative decrease in intrinsic fluorescence intensity of Pectinex® Ultra Clear (PUC) and Pectinex® Ultra SPL (PUS) after ultrasonic treatment was approximately 51% and 55%, respectively, while the decrease induced by thermal denaturation was 25% and 30% respectively. Furthermore, a blue shift in the fluorescence spectrum of both pectinases was observed upon sonication for all process conditions indicating a change in enzyme conformation. However, ultrasonic treatment did not result in a significant change in enzyme activity, suggesting that these conformational adjustments may occur in regions other than the active sites. Moreover, ultrasonicated pectinases and cellulases did not exhibit any improvement in their catalytic potential under either optimal or non-optimal conditions.
This paper provides an overview on steered fermentation processes to release phenolic compounds from plant-based matrices, as well as on their potential application to convert phenolic compounds into ...unique metabolites. The ability of fermentation to improve the yield and to change the profile of phenolic compounds is mainly due to the release of bound phenolic compounds, as a consequence of the degradation of the cell wall structure by microbial enzymes produced during fermentation. Moreover, the microbial metabolism of phenolic compounds results in a large array of new metabolites through different bioconversion pathways such as glycosylation, deglycosylation, ring cleavage, methylation, glucuronidation and sulfate conjugation, depending on the microbial strains and substrates used. A whole range of metabolites is produced, however metabolic pathways related to the formation and bioactivities, and often quantification of the metabolites are highly underinvestigated. This strategy could have potential to produce extracts with a high-added value from plant-based matrices.
The potential of selected industrial food wastes from juice and nut production including apple peel, apple pomace, pomegranate peel, pomegranate seed, chestnut shell, and black carrot pomace as ...resources for natural antioxidants was investigated. Soluble free and insoluble-bound phenolics were extracted from the wastes and analyzed for total phenolic and flavonoid contents, phenolic profile and antioxidant activity. Total phenolic and total flavonoid contents of wastes were positively correlated with their antioxidant activity. The highest total phenolic and antioxidant activity were determined in soluble fraction of pomegranate peel due to a significant amount of punicalagin derivatives. Pomegranate peel and seed had the most phenolics and flavonoids in soluble form while other wastes had more than 45% of total phenolics in insoluble-bound form. Chestnut shell showed more antioxidant activity in insoluble-bound fraction compared to that of its soluble fraction. These findings showed that not only soluble but also an insoluble-bound fraction of the industrial wastes has good potential for valorization as a source of natural antioxidants.
Abstract
Flavonoids are a group of polyphenols that provide health-promoting benefits upon consumption. However, poor bioavailability has been a major hurdle in their use as drugs or nutraceuticals. ...Low bioavailability has been associated with flavonoid interactions at various stages of the digestion, absorption and distribution process, which is strongly affected by their molecular structure. In this review, we use structure-activity/property relationship to discuss various flavonoid interactions with food matrices, digestive enzymes, intestinal transporters and blood proteins. This approach reveals specific bioactive properties of flavonoids in the gastrointestinal tract as well as various barriers for their bioavailability. In the last part of this review, we use these insights to determine the effect of different structural characteristics on the overall bioavailability of flavonoids. Such information is crucial when flavonoid or flavonoid derivatives are used as active ingredients in foods or drugs.
Phytate, phenolic compounds and fiber are known anti-nutritional factors (ANFs) that contribute to the low bioaccessibility and bioavailability of iron and zinc in plant foods. Better insight into ...the localization of minerals and anti-nutritional factors in plant tissues, as well as on the mechanisms of interaction between minerals and ANFs, may lead to better targeted processing for improvement of the bioaccessibility of minerals in plant foods. This review highlights the subcellular distribution of iron and zinc and their ANFs in plant organs, as well as the mechanisms of interaction between these metals and their ANFs. These insights are then used to better clarify the role of various processing technologies, like mechanical treatments, soaking, germination, fermentation and heating, on improving the bioaccessibility of iron and zinc in plant foods.
•Different anti-nutritional factors (ANFs) may act simultaneously on mineral bioaccessibility.•Localization of minerals and their ANFs in plants can influence mineral bioaccessibility.•Mineral location and type of interaction with ANFs may influence the effect of processing.
A total of 92 marine bacteria belonging to
Pseudomonas
,
Pseudoalteromonas
,
Psychrobacter,
and
Shewanella
were first screened for their proteolytic activity. In total, four
Pseudomonas
strains ...belonging to
Ps. fluorescens
,
Ps. fragi
,
Ps. gessardii,
and
Ps. marginalis
; 14
Pseudoalteromonas
strains belonging to
Psa. arctica, Psa. carrageenovora, Psa. elyakovii, Psa. issachenkonii, Psa. rubra, Psa. translucida,
and
Psa. tunicata
; and two
Shewanella
strains belonging to
S. baltica
and
S. putrefaciens
were identified to have a weak to high proteolytic activity (from 478 to 4445 mU/mg trypsin equivalent) against skim milk casein as protein source. Further chitinolytic activity screening based on these 20 proteolytic strains using colloidal chitin yielded five positive strains which were tested against three different chitin substrates in order to determine the various types of chitinases. Among the strains that can produce both proteases and chitinases,
Psa. rubra
DSM 6842
T
expressed not only the highest proteolytic activity (2558 mU/mg trypsin equivalent) but also the highest activity of exochitinases, specifically, β-N-acetylglucosaminidase (6.33 mU/10
7
cfu) as well. We anticipate that this strain can be innovatively applied to the valorization of marine crustaceans side streams.
Water quality in the drinking water system (DWS) plays an important role in the general health and performance of broiler chickens. Conditions in the DWS of broilers are ideal for microbial biofilm ...formation. Since pathogens might reside within these biofilms, they serve as potential source of waterborne transmission of pathogens to livestock and humans. Knowledge about the presence, importance and composition of biofilms in the DWS of broilers is largely missing. In this study, we therefore aim to monitor the occurrence, and chemically and microbiologically characterise biofilms in the DWS of five broiler farms.
The bacterial load after disinfection in DWSs was assessed by sampling with a flocked swab followed by enumerations of total aerobic flora (TAC) and Pseudomonas spp. The dominant flora was identified and their biofilm-forming capacity was evaluated. Also, proteins, carbohydrates and uronic acids were quantified to analyse the presence of extracellular polymeric substances of biofilms. Despite disinfection of the water and the DWS, average TAC was 6.03 ± 1.53 log CFU/20cm
. Enumerations for Pseudomonas spp. were on average 0.88 log CFU/20cm
lower. The most identified dominant species from TAC were Stenotrophomonas maltophilia, Pseudomonas geniculata and Pseudomonas aeruginosa. However at species level, most of the identified microorganisms were farm specific. Almost all the isolates belonging to the three most abundant species were strong biofilm producers. Overall, 92% of all tested microorganisms were able to form biofilm under lab conditions. Furthermore, 63% of the DWS surfaces appeared to be contaminated with microorganisms combined with at least one of the analysed chemical components, which is indicative for the presence of biofilm.
Stenotrophomonas maltophilia, Pseudomonas geniculata and Pseudomonas aeruginosa are considered as opportunistic pathogens and could consequently be a potential risk for animal health. Additionally, the biofilm-forming capacity of these organisms could promote attachment of other pathogens such as Campylobacter spp. and Salmonella spp.
In this study, 22 phenolic compounds were investigated to inhibit the angiotensin-converting enzyme (ACE). Tannic acid showed the highest activity (IC50 = 230 μM). The IC50 values obtained for ...phenolic acids and flavonoids ranged between 0.41 and 9.3 mM. QSAR analysis confirmed that the numbers of hydroxyl groups on the benzene ring play an important role for activity of phenolic compounds and that substitution of hydroxyl groups by methoxy groups decreased activity. Docking studies indicated that phenolic acids and flavonoids inhibit ACE via interaction with the zinc ion and this interaction is stabilized by other interactions with amino acids in the active site. Other compounds, such as resveratrol and pyrogallol, may inhibit ACE via interactions with amino acids at the active site, thereby blocking the catalytic activity of ACE. These structure–function relationships are useful for designing new ACE inhibitors and potential blood-pressure-lowering compounds based on phenolic compounds.
Enzymatic browning of Iceberg lettuce was studied by subjecting midrib tissues to a series of mild heat treatments. The effects of wounding and subsequent application of a mild heat treatment were ...examined by monitoring the browning potential (BP) and the activity of three browning‐related enzymes (i.e., phenylalanine ammonia lyase PAL, polyphenol oxidase PPO, and peroxidase POD) during refrigerated storage up to 10 days. Efficient inhibition of browning was achieved by treatment at 50°C for 60 s. The wound‐induced increase of the BP and the activity of PAL and POD was effectively suppressed, maintaining their values at initial levels up to 7 days of storage. PPO activity, on the contrary, remained unchanged after wounding, whether or not followed by heat treatment. BP, PAL activity and POD were found to be strongly correlated, whereas meaningful associations for PPO with the other parameters could not be established.
Practical applications
In an attempt to answer to the growing demand in the fresh‐cut produce industry to control browning, heat treatment was investigated as interesting alternative to chemical preservation methods. Efficient control of enzymatic browning in fresh‐cut Iceberg lettuce could be achieved by heat treatment at 50°C for 60 s. Experimental data are provided showing the effects of wounding and subsequent heat treatment on visual browning, the BP and the activity of PAL, PPO, and POD during refrigerated storage up to 10 days. Using this data, correlations were found for BP, PAL activity, and POD activity, but not for PPO. Although undesired side effects of heat treatment (e.g., tissue softening) cannot be excluded, the obtained information might be useful for further research, serving as a baseline for wound‐induced effects on browning‐related parameters in fresh‐cut lettuce and possible mechanisms of action of inhibitory treatments.
Heat treatment at 50°C for 60 s was found to be most efficient to inhibit enzymatic browning of fresh‐cut Iceberg lettuce during storage. Heat treatment suppressed the wound‐induced increase of the browning potential and the activity of PAL and POD, while PPO activity remained unchanged. Correlations were found for the browning potential and the activity of PAL and POD.
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