Colour analysis of potential natural colourant from Ixora siamensis and Melastoma malabathricum

Anthocyanins are an important group of natural pigments that are responsible for many colours in plants. The variation in colour, depending on the pH, makes them a unique source of natural colourant. In this study, pigments from the fruits of Ixora siamensis and the fruit pulps of Melastoma malabathricum were extracted using trifluoroacetic acid-methanol solution. Spectral measurements (380-780 nm) were performed using visible spectroscopy with colour analysis software at different pHs (initial extracts were 1, 5, 7, 9 and 11). The colours of the solutions were expressed as colourimetric coordinates in the Commission Internationale de l'Eclairage (CIE) laboratory scale using L* (lightness), C* (chroma), H degrees (hue angle notation hab), a*/-a* (redness and greenness) and b*/-b* (blueness and yellowness) for the D65/2 degrees CIE Illuminant/Observer condition. In this work, the colour parameters were observed for natural colourant with and without blending with polyvinyl alcohol for both species (Ixora siamensis and Melastoma malabathricum). The relationships between the colour parameters (colourimetric indexes and CIELab variables) with pH variation and species dependence were discussed in this paper

Study of anthocyanin stability derived from the fruit pulp of Melastoma malabathricum in a coating system

Purpose - The purpose of this paper is to evaluate the stability of anthocyanin colorant with and without ferulic acid (FA) stabilising agent in a polyvinyl alcohol (PVA) binder coating system. Design/methodology/approach - The anthocyanin colorant was extracted using methanol acidified with 0.5 trifluoroacetic acid (TEA). FA was added to improve thermal stability of the colorant. The FA added colorant was mixed with PVA to develop a coating system. To test the ability of the coating mixture to withstand heat in the liquid state, spectroscopic studies were carried out in the visible region of the electromagnetic spectrum when the liquid samples had cooled down to room temperature after being heated at 80 and 90 degrees C for 30 minutes. This procedure was repeated six times until a total heating time of 180 minutes has been accomplished. The liquid samples were also coated on glass slides, cured and then stored in different incubators at 30, 40 and 50 degrees C. The visible spectrum was taken everyday for 30 days to study the effect of storage temperature. Spectroscopic results were analysed in terms of intensity rate percentage (IRP). Findings - In the liquid state, the anthocyanin-PVA mixture without FA showed lower absorbance compared to the mixture containing FA after heating at 80 and 90 degrees C. This shows that FA can enhance the intensity of absorbance of the liquid coating mixture. The mixtures containing FA show increase in absorbance with increase in heating time. The same results are obtained for the coating on glass substrate where FA containing coatings show increase in IRP with time for all storage temperatures. Coating with 1 FA content showed better enhancement and stability. Research limitations/implications - The colour of the untreated samples quickly faded during heating and storage at different temperatures. In this study, the addition of 0.5 and 1 FA stabilised and enhanced the colour intensity at 30, 40 and 50 degrees C. Further improvements may find the mixture suitable as paint or coating materials and as nail varnish. Practical implications - The results indicate the possibility of applying the FA stabilised anthocyanin-PVA, colorant-binder composition in a coating system. Originality/value - The use of anthocyanin from M. Malabathricum as a colourant in a coating system or nail varnish is original. Anthocyanin pigments are normally used as colorant in foods

Effects of UV-B irradiation on poly (vinyl alcohol) and Ixora siamensis anthocyanins-coated glass

Purpose - The purpose of this paper is to evaluate the potential of natural colourants from fruits of Ixora siamensis for coating applications, to study its glossiness and effectiveness against UV-B irradiation. Design/methodology/approach - In this study, natural colourants from the fruits of Ixora siamensis were extracted using trifluoroacetic acid-methanol solution. Anthocyanins and organic acid variants were mixed together to form co-pigments. Different concentrations of ferulic and gallic acid co-pigments were added to a blended solution of poly (vinyl alcohol), PVA and anthocyanin (from Ixora siamensis) to form a coating system. The coatings were exposed to UV-B irradiation at room temperature in air using a UV-lamp which emitted radiation at 312 nm. The effects of UV-B irradiation on the coating system were evaluated using glossiness test and UV-visible spectroscopy. Findings - Anthocyanins are unstable and can quickly lose their colour. One of the methods of preserving the stability of these pigments is by co-pigmentation. Co-pigmentation of anthocyanin with organic acid variants resulted in an increase in both hyperchromic effects (Delta A) and bathochromic shifts (A lambda). In this study, ferulic acids yielded better results compared to gallic acids. Research limitations/implications - Samples with co-pigmentation give better result compared to the untreated samples. The addition of 0.5 and 1.0 per cent ferulic acid improves the gloss properties and resistivity of the samples towards the UV irradiation. Thus, in order to study the effectiveness of ferulic acid as additive and improving the properties of the samples, the percentage of ferulic acid added and exposure time could be increased. Practical implications - The method developed provided a simple and efficient solution for improving the UV resistance of anthocyanin blend with poly (vinyl alcohol), PVA UV absorber. Effect of ferulic acid as UV absorber, if added in more concentration, can be further studied for optimization. Social implications - The social implication is the use of local plant species as a low cost source of natural pigments in coating system. Originality/value - The method for improving the resistance towards UV irradiation of anthocyanin blend with poly (vinyl alcohol), PVA was novel and could find numerous applications for natural product based on plant pigment

Colour properties of poly(vinyl alcohol)–anthocyanin blends

This work aims to analyze the colour variation and stability of anthocyanin colourant. Anthocyanin has been solvent-extracted from fruit pulps of Melastoma malabathricum. Different weight percentage of ferulic acid (FA) have been added to the anthocyanin solution and exposed to 17.55 lux UV-B irradiation for 93 days. The colour stability has been evaluated using Commission Internationale de l’Eclairage (CIE) colour system. The FA has been added to anthocyanin solution that contains.5 % trifluoroacetic acid (TFA) has been mixed with poly (vinyl alcohol) or PVA for the development of a coating system. The PVA–anthocyanin coating without FA has the most unstable colour. Coating with 3 % FA addition resulted in better colour stability. Colour stability has been analysed via lightness (L*), chromaticity(c*), hue angle (H°), coordinates a* and b* as well as colour saturation

Natural populations of lactic acid bacteria in douchi from Yunnan Province, China*

This research was aimed at isolating and identifying the predominant lactic acid bacteria (LAB) in the traditional Chinese salt-fermented soybean food, douchi, from Yunnan, China. The predominant LAB present were isolated and identified by conventional culture-dependent methods combined with molecular biological methods. Two hundred and sixty isolates were obtained from thirty kinds of traditional fermented douchi from six cities and counties in Yunnan, and those strains were divided into twelve groups by their morphological and biochemical characteristics. Based on 16S ribosomal DNA (rDNA) sequencing and analysis, 56 representative strains were identified as belonging to 6 genera and 14 species: Lactobacillus (4 spp.), Weissella (3 spp.), Pediococcus (2 spp.), Staphylococcus (2 spp.), Enterococcus (1 sp.), and Bacillus (2 spp.). The results show that douchi contains a large natural population of LAB of diverse composition from which some strains could be selected as starters for functional fermented foods. This is the first study on the original douchi from Yunnan, and the results suggest that it may be a useful source for the isolation of LAB. This study has also laid a foundation for further research on developing functional douchi products