Effects of Transition Metal Ions on the Colour of Blue-Green Beryl

This study reports the effects of transition metal ions on the colour of blue-green beryl. Industrial cameras were used to measure colour in the CIELAB colour space. X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), and ultraviolet-visible (UV–vis) spectroscopy were used for characterization. The d–d transition of Fe3+ with sixfold coordination, the O2−→Fe3+ charge transfer, and the charge transition of binuclear metal M–M complexes formed by [Fe2(OH)4]2+ in the channel caused a yellow tone, whereas the charge transfer of Fe2+/Fe3+ with sixfold coordination caused a blue-green tone. The chroma of blue-green beryl was negatively correlated with the ratio of Cs+Mn to Fe contents. The lightness of blue-green beryl was negatively correlated with the total content of transition metal ions.

Mass Transfer and Optical Properties of Active PET/PP Food-Grade Films Impregnated with Olive Leaf Extract

A supercritical solvent impregnation (SSI) technique was employed to incorporate, by batch- and semicontinuous-modes, bioactive olive leaf extract (OLE) into a food-grade multilayer polyethylene terephthalate/polypropylene (PET/PP) film for active food packaging applications. The inclusion of OLE in the polymer surfaces significantly modified the colour properties of the film. A correlation of 87.06% between the CIELAB colour parameters and the amount of the OLE impregnated in the film was obtained which suggests that colour determination can be used as a rapid, non-destructive technique to estimate the OLE loading in the impregnated matrices. The UV barrier and water permeability properties of the films were not significantly modified by the incorporation of OLE. The migration of OLE into a 50% (v/v) ethanol food simulant demonstrated faster release of OLE from the PP surface than from the PET surface which may be due to the different interactions between OLE and each polymer.

Correlation between CIELAB colour coordinates and malondialdehyde eqiuvalents in sausage with paprika stored under refrigerated conditions

Sensory properties of foods mainly affect purchasing decisions. In case of sausages, deterioration of pigments of meat and spices cause discolouration, while lipid oxidation leads to the formation of off-odours, and these two processes are connected. Lipid oxidation promotes the conversion of pigments, while the formation of metmyoglobin accelerates lipid oxidation. The scope of the study was to investigate the relationship between the amount of malondialdehyde equivalents (MDA) and CIELAB colour coordinates in a Hungarian sausage with paprika, sliced and stored under refrigerated conditions for 10 weeks. We detected negative correlation (P < 0.001) between the MDA-level and a* and b*; and positive correlation (P < 0.001) between the MDA-level and L*. The observed correlation between MDA level and colour coordinates supports the assumption that the oxidation of lipids and pigments are interrelated in the case of sausage with paprika.

Predicting the colour associated with odours using an electronic nose

Predicting olfactory perception with an electronic nose can aid in the design and evaluation of olfactory-based experiences. We investigate whether the human perception of odours can be predicted outside the bounds of perceived pleasantness and semantic descriptors. We tuned an electronic nose to predict an odour's colour in the CIELAB colour space using human judgements. This revealed that the crossmodal associations people have towards colours could be predicted. Our electronic nose system can predict an odour's colour with a 70 – 81% machine-human similarity rating. These findings suggest a systematic and predictable link exists between the chemical features of odours and the colour associated to them. These findings highlight the possibilities of predicting human olfactory perception using an electronic nose.

Impacts of added oenological tannins on red wine quality to counteract Botrytis infection in Merlot grapes

The contamination of grape berries by Botrytis cinerea can drastically damage wine quality, in particular causing colour degradation. In musts obtained from botrytised grapes, SO2 addition is the main means of avoiding oxidation damage due to laccases excreted by the pathogen. However, consumers are becoming increasingly reluctant to accept SO2 addition to wine. Oenological tannins are used for fining wines because of their colloidal properties, and for wine colour stabilisation due to their ability to condense with anthocyanins. They are also known for their antioxidant and antioxidasic properties. They were thus investigated in the present study for their potential as an alternative to SO2 against laccase oxidation.The impact of various types of oenological tannins on musts and wines was studied once added to musts obtained from the Merlot cultivar, comprising 20 % and 50 % botrytised grapes. Laccase activity, antioxidant capacity, composition of phenolic compounds, spectrophotometric and CIELAB colour parameters were assessed in the musts and wines. Sensory analyses were also performed on 3-month-old wines to evaluate the visual, olfactory and gustative consequences of tannin addition. At a 50 % botrytisation rate, the addition of any type of oenological tannins (at a concentration of 100 g/hL) had no effect on laccase activity and did not protect phenolic compounds. However, at the same concentration and at a 20 % botrytisation rate, proanthocyanidin tannins from grape skin were found to be the most promising tannins with simultaneous protective effects, such as an inhibitory effect on laccase enzymes, protection of colour from complete degradation and preservation of some procyanidin compounds.Oenological tannins are promising candidates for protecting wines from Botrytis damage and they induce a differential effect according to their origin and structure. They could be used to reduce the amount of SO2 that is added during vatting. More research is needed to confirm and better understand the mode of action of various tannins at levels lower than the 20 % botrytised rate tested in the present study.

Fabrication of smartphone-based colorimetric device for detection of water leaks

South Africa is a water-scarce country due to the shortage of rainfall. This scarcity is further exacerbated by the loss of water through leakage from faulty pipes. This paper reports on the use of a simple microfluidic device in the early detection of water leakages. The microfluidic paper-based device (µPADs) were prepared by printing patterns of wax (100 μm width) on the paper surface and melting the wax into the paper to form hydrophobic barriers. Solutions of lower to higher pH were also prepared and were introduced to the chlorophenol red test strips and a range of colours from yellow (lower pH) to purple (higher pH) were obtained. The digital images obtained with the μPADs were analysed using the CIELab colour system. The optimized pH range was wider than the typical grayscale-based image analysis and was successful for a wide pH range of 2–12. The QR codes attached to the strips enable tracking to obtain the real-time location from which leakage was detected. The study conclusively shows that the combination of digital image analysis and a μPAD device is highly efficient for quantitative analysis, and thus useful for the detection of household water leaks.

Assessment of Rosemary (Rosmarinus officinalis L.) Extract as Antioxidant in Jelly Candies Made with Fructan Fibres and Stevia

Enrichment with rosemary antioxidants is proposed as a possible strategy to obtain healthier jelly candies. Two aqueous rosemary extracts (RE) containing 73.9 (RE74) and 145.6 (RE146) mg polyphenols per g fresh weight were assessed as antioxidants in jelly candies based on fructooligosaccharides, inulin and stevia. Up to 15 phenolic acids, flavonoids and diterpenes were determined in the extracts, with rosmarinic acid as the main active compound. Sensory tolerance, physical properties, rosmarinic acid recovery, polyphenol content, and antioxidant capacity were determined in jelly candies. The threshold of sensory detection was established at 0.26 g RE146/kg of raw candy, below which rosemary off-flavours were avoided without altering pH, brix, texture, CIELab colour, and consumer acceptance. Adding 0.26 g RE146 per kg increased (p < 0.001) polyphenol content from 197 to 411 µg GAE/g and the antioxidant capacity from 1.77 to 4.14 μmol Trolox/g. Rosemary polyphenols resulted in being resistant to cooking, acted as secondary antioxidants and showed good interaction with the other jelly ingredients. Aqueous extracts from rosemary distillation by-products can be incorporated at acceptable levels to jelly candy formulations leading to higher oxidative stability and an increased content of dietary polyphenols.

A colorimetric comparison of sunless with natural skin tan

The main ingredient of sunless tanning products is dihydroxyacetone (DHA). DHA reacts with the protein and amino acid composition in the surface layers of the skin, producing melanoidins, which changes the skin colour, imitating natural skin tan caused by melanin. The purpose of this study was to characterise DHA-induced skin colour changes and to test whether we can predict the outcome of DHA application on skin tone changes. To assess the DHA-induced skin colour shift quantitatively, colorimetric and spectral measurements of the inner forearm were obtained before, four hours and 24 hours after application of a 7.5% concentration DHA gel in the experimental group (n = 100). In a control group (n = 60), the same measurements were obtained on both the inner forearm (infrequently sun-exposed) and the outer forearm (frequently sun-exposed); the difference between these two areas was defined as the naturally occurring tan. Skin colour shifts caused by DHA tanning and by natural tanning were compared in terms of lightness (L*), redness (a*) and yellowness (b*) in the standard CIELAB colour space. Naturalness of the DHA-induced skin tan was evaluated by comparing the trajectory of the chromaticity distribution in (L*, b*) space with that of naturally occurring tan. Twenty-four hours after DHA application, approximately 20% of the skin colour samples became excessively yellow, with chromaticities outside the natural range in (L*, b*) space. A principal component analysis was used to characterise the tanning pathway. Skin colour shifts induced by DHA were predicted by a multiple regression on the chromaticities and the skin properties. The model explained up to 49% of variance in colorimetric components with a median error of less than 2 ΔE. We conclude that the control of both the magnitude and the direction of the colour shift is a critical factor to achieve a natural appearance.

Effect of Hairiness on Fabric Colour Characteristics

Designing the colour appearance of textiles requires taking into account their surface properties, hairiness among others. The villi protruding on the surface not only affect the quality of textile dyeing, but also largely determine its optical properties and the colour phenomenon. The analysis of studies of optical properties shows that the influence of hairiness on the phenomenon of colour is not well understood and that the amount of hairiness at which colour changes become significant for human perception remains indefinable. In this work, we studied the change in colour characteristics depending on the change in the hairiness of woollen fabrics, comparing “yarn – raw fabric”, “yarn – raised fabric”, “raw fabric – raised fabric”. Hairiness was estimated by the hairiness index, which was obtained from the analysis of sample microphotographs of yarn and fabric using software. The value of colour characteristics (lightness, chroma and colour difference) was measured in the CIELAB colour space (1976) using a spectrophotometer. The obtained experimental results showed that the changes in lightness and saturation of textile materials from the index of its hairiness are directly proportional. However, the value of changes is different for raw and napped fabrics, undyed and dyed samples, the initial colour hue and raw material composition also making certain adjustments. This study analysed the colour difference and established the level of variation in hairiness at which the colour mismatch between woollen fabrics becomes visually noticeable. The results of the study can be used to predict the colour and design the optical properties of fabrics for weaving and finishing.

Preferred skin reproduction centres for different skin groups

Producing preferred skin colours is vital for the digital images on mobile phone manufacturers. Previous studies investigated the skin colours only in chromatic plane excluding lightness. A psychophysical experiment was conducted to determine preferred skin colour centres for different skin colour types on mobile displays in a darkened room. Ten facial images were selected for the experiment to cover different skin colour types (Caucasian, Oriental, South Asian and African). A set of 49 predetermined colour centres uniformly sampled within the skin colour ellipsoid in CIELAB colour space was used to morph skin colours of test images. Thirty observers from each of the 3 ethnic groups (Caucasian, Oriental and South Asian) participated in the experiment. The preferred skin colour centre and region in the form of ellipsoid for each skin group were reported. It was found that the preferred colour centres from different skin colour types were very similar except their lightness as expected, and were also quite similar between the observers from different ethnic groups.