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This study aims to develop a green, economical and efficient ultrasonic-/microwave assisted extraction (UMAE) process for the extraction of anthocyanins.

After optimizing the extraction conditions by response surface methodology, three assays including DPPH, ABTS·+, FRAP were applied to analyze the antioxidant activity of the extracted anthocyanins. The stability under different temperatures, reductant concentrations and pHs was also discussed. The components of anthocyanins in blueberry were analyzed by HPLC-QTOF-MS2.

The optimal extraction parameters were ultrasonic power of 300 W, microwave power of 365.28 W and solid–liquid ratio of 30 (g/mL). The possible structures can be speculated as Delphinidin-3-O-galactoside, Delphinidin, Petunidin, Delphinidin-3-O-glucoside, Petunidin-3-O-glucoside, Cyanidin-3-O-glucoside. The results demonstrated that the UMAE can improve the yield of anthocyanins in shorter extraction time with higher activity.

The present study may provide a promising and feasible route for extracting anthocyanins from blueberries and studying their physicochemical properties, ultimately promoting the utilization of blueberry anthocyanins.

The purpose of this paper is to observe the colour and thermal stability of natural red dye consisting of anthocyanin with addition of different aqueous acids and applied as coating films.

The natural red dye was extracted from Hibiscus sabdariffa L. (roselle) flowers and mixed with 1 per cent hydrochloric acid, 5 per cent acetic acid, 5 per cent citric acid and 5 per cent oxalic acid. All the dye samples were exposed to heat and UV-B to observe the colour stability by calculating the half-life and rate of reaction. In coating film application, each of the dye samples was mixed with 25 wt% of poly(vinyl alcohol) (PVA) and applied on to a glass substrate. The coating samples’ colour stability was observed by using CIE L*a*b* colour space coordinates. The coating films’ weight loss stability against temperature was observed by using thermogravimetric analysis.

Addition of hydrochloric acid enhances the thermal and UV stability of the anthocyanin natural dye. This can be observed from the calculation of the half-life of the dye. The half-life values for the thermal and UV stability studies were 1,155 hours and 210 hours, respectively. In coating films, the sample with addition of acetic acid showed the highest colour stability with colour difference (ΔE*) value 8.95.

The coating films developed in this work are not suitable to be applied on metal substrates due to the presence of water, which can contribute to the corrosion formation.

The coating films developed in this work are suitable for washable coating application. In other words, they are non-permanent coatings applied on a glass substrate.

Development of water-based coatings from PVA binder with anthocyanin colourant is introduced in this study.

The purpose of this paper is to develop a new water based coating system composed of poly(acrylamide‐co‐acrylic acid) and anthocyanin colourant extracted from Hibiscus sabdariffa L. and characterise the system.

Anthocyanin from Hibiscus sabdariffa L. (roselle) calyxes was extracted using optimised water extraction method with ratio of calyxes to water being 1:2. UV‐Vis absorption spectroscopy was conducted on the anthocyanin extract to monitor its degradation. Poly(acrylamide‐co‐acrylic acid) was mixed with the extracted anthocyanin solution in two different weight ratios. The mixtures were coated on glass substrate and let to cure for approximately one day. FTIR spectroscopy was conducted on the samples to determine their functional groups and identify the compounds in the samples. Cross hatch test was performed on the samples to determine the adhesion properties. Thermal degradation of the samples was determined through thermogravimetric analysis. Surface roughness of the samples was studied by atomic force microscopy. Colour stability was determined before and after UV irradiation.

Anthocyanin pigment from roselle extracted with water was found to be stable with 6.0 per cent drop in absorbance value over the 15 day period. The reaction rate was found to be 0.000181 h⁻¹, and the half life was calculated to be 3,850 hours. Better adhesion of the samples to the glass substrate was due to the higher concentration of poly(acrylamide‐co‐acrylic acid). Thermogravimetric analysis revealed similar thermal stability of the samples. Surface roughness study revealed that sample with higher anthocyanin content has higher surface roughness. Colour stability of the 20PBR was found to be better than 10PBR.

Usage of poly(acrylamide‐co‐acrylic acid) as coating is limited by its weak water resistance property. Improvement could be made in this direction for future applications.

Mixture of water‐based polymer and anthocyanin colourant from roselle has been developed into coating for the first time. Commercialisation is possible if more research is conducted towards water resistance property of poly(acrylamide‐co‐acrylic acid), storage condition for the pigment and coating, and mass production of the pigment.

Incorporation of anthocyanin pigment into water based coating is the first of its kind.

The aim of this study was to evaluate the effect of ultrasound (US) treatment on the postharvest of “Isabella” grapes and the consistency of the obtained results regarding the composition of anthocyanins in grape juice over three successive harvest years using a combination of analytical techniques.

Juices produced from “Isabella” grapes sonicated for different durations (3, 5, 7 and 10 min) were analysed. The grapes were harvested and sonicated in 2013, 2014 and 2015, and each treated sample was stored for 1, 3 and 5 days in order to verify the time necessary for the development of the US response. The juices were analysed through physicochemical analysis (total monomeric anthocyanins). The anthocyanin profiles were quantified and identified using high performance liquid chromatography coupled to photodiode array and mass spectrometry detectors (HPLC-PDA-MSn).

The results demonstrated the potential of US in improving the quality of grape juice. In all three harvests, it was observed that the treatments were effective in increasing the concentration of anthocyanins. For the 2013 harvest, the application of US for 5 min led to a 103% increase in juice pigments. However, the US response profile varied among the three harvests, indicating that the US effect was influenced by the ripening conditions of the fruit. In total, 33 anthocyanins were identified in the grape juice. For the first time, peonidin-3-p-coumaroyl glucoside-5-glucoside was identified in “Isabella” juice.

The results of this study validated US treatment as a simple and effective physical method that can be used as an alternative technology for improving the general quality of products such as juice by increasing the pigment concentrations that are linked to the colour and antioxidant potential of drinks. Moreover, the results demonstrate that US treatment may be less effective in the case of a sample with distinct phenolic maturation.

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.

The anthocyanin colorant was extracted using methanol acidified with 0.5% trifluoroacetic acid (TFA). 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°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°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).

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°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.

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°C. Further improvements may find the mixture suitable as paint or coating materials and as nail varnish.

The results indicate the possibility of applying the FA stabilised anthocyanin‐PVA, colorant‐binder composition in a coating system.

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.

The purpose of this research is to identify and investigate some natural dyes with halochromic properties for potential use as food spoilage indicators to reduce waste and curve the negative effects of food borne diseases.

Exactly 10 potential dye-yielding plants were selected based on their colour (mostly purple, red, maroon and pink). Solvent extraction was used to extract the dyes and pH differential method was used to determine the concentrations of anthocyanin in the extracted dyes. Different concentrations of hydrochloric acid and sodium hydroxide (0.1 M, 1 M and 2 M) in drops and in excess as acidic and basic solution, respectively, were used to test the halochromicity of the extracted dyes. Methyl red (a synthetic dye) was used as a reference standard/control. The pH of the dyes was recorded before and after addition of both NaOH and HCl solutions.

Five out of the 10 dyes extracted (labelled as dye A–E for Ti plant (green Cordyline fruticosa), coleus (Coleus blumei), paper flower (Bougainvillea glabra), painted nettle (Palisandra coleus) and purple heart (Setcresea purpurea), respectively, were found to be halochromic (even at low doses) by changing its colour when exposed to both acidic and basic solutions. While other dyes labelled F–J for red acalypha (Acalypha wilkesiana), golden shower (Cassia fistula), golden dew drop (Duranta repens), wild sage (Lantana camara var Aculeata) and pink oleander (Apocynaceae Nerium oleander), respectively, were either completely insensitive to the solutions in drops, slightly sensitive at high doses or the colour change is insignificant. Although some dyes were found to be more sensitive than others but in most cases, the colour changes in halochromic dyes were more stable in acidic conditions than in basic making it more sensitive to the basic than the acidic solution with the exception of dye A and E (to some extent) which was sensitive to both acidic and basic solution. The anthocyanin contents of dye A–J were found to be between the range of 2.28–10.35 mg/l with dye E having the lowest and dye J with the highest anthocyanin concentration, respectively. The initial pH of all the dyes falls within the range of 4.8–7.3 with most found within the acidic range.

Halochromic dye research studies are still at the infancy stage in developing world despite the vast available and abundant potential natural halochromic dye-yielding plants. The study explored this area of research and gives an opportunity for the development of smart packaging for pH-sensitive foods using natural dyes as an alternative to conventional synthetic dyes to reduce cost and also curve the negative effect of synthetic dyes as well as food borne diseases.

Anthocyanins. The anthocyanin pigments impart the pleasing red and purple colours associated with many fruits and vegetables. They belong to the class of compounds referred to as ‘flavonoids’ and, in chemical terms, they are flavylium salts differing in the number and position of free or methylated hydroxyl groups and with a sugar moiety linked through position 3 or positions 3 and 5 in the ring. A commonly occurring anthocyanin pigment, cyanidin‐3‐glucoside, is shown in figure 3. The anthocyanins are soluble in water and are unstable under a variety of enzymic and non‐enzymic conditions.

The purpose of this study is to investigate the effects of pH, UV-B radiation and NaCl on anthocyanin extracted from vivid blue petals of Clitoria ternatea L. (legume crop), as a potential natural colourant for food, dye or coating technology.

The anthocyanin from petals of Clitoria ternatea was extracted using 0.5 per cent trifluroacetic (TFA) in methanol solution. The liquid colourant was exposed to different pH (1, 4.5 and 5.5), UV-B radiation and sodium chloride (NaCl). The results were compared using UV-vis spectrophotometric analysis.

Anthocyanins are sensitive and quickly degrade in the presence of light. In the dry powder form, the anthocyanin is easier to maintain and preserve (storage).

Anthocyanins extracted from vivid blue petals of Clitoria ternatea L. are sensitive and quickly degrade in the presence of light.

The anthocyanin pigments extracted from Clitoria ternatea L. petals with methanolic acid were successfully coated on glass slides. The combination of binders and pigments had produced environmental paint which added with stabilisers (additives) for better durability. Acrylic has been known for its high weathering and embrittlement resistance, good mechanical and electrochemical properties and gloss retention.

This anthocyanin is suitable as natural colourant especially in baby products, cosmetics production or for coating and varnish application.

Till date, the natural colourant of Clitoria ternatea L. petals is widely used in food. However, this result is a new finding, as there is no report on the potential of applications of this natural colourant for coating technology. Therefore, the current study with appropriate extraction method was significantly based on the relevant literatures of coating production from pigment by using other plant species. The findings and conclusion highlight the practicality as the potential applications in coating technology.

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.

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.

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 (ΔA) and bathochromic shifts (Δλ). In this study, ferulic acids yielded better results compared to gallic acids.

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.

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.

The social implication is the use of local plant species as a low cost source of natural pigments in coating system.

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.

Phenolic compounds play a critical role in grape quality, and their content is strongly influenced by bunch zone temperature during the ripening period. The mechanism of responding to temperature was found to highly depend on cultivars. The present study aimed to evaluate the effects of row orientation and canopy side on phenolic content in grape berries.

The authors analyzed the accumulation of phenolic compounds in mature berries of Cabernet Sauvignon and Cabernet Gernischt. They were harvested from various canopy sides of north-south and east-west row orientations, which were NS–E and NS–W, EW–S and EW–N.

During the ripening period, mean temperatures of the bunch zones, NS–W and EW–N were respectively higher than NS–E and EW–S. At harvest, the total phenolic, total anthocyanin, tannin and reducing sugar contents were higher in NS–E and EW–S, than in NS–W and EW–N, respectively, indicating a negative relationship with temperature. For both varieties, EW–S had the highest proportion of malvidins anthocyanins. Peonidins, delphinidins, and cyanidins anthocyanins of EW–N showed a higher ratio in Cabernet Sauvignon, while NS–E showed a higher ratio in Cabernet Gernischt.

To improve grape monomeric anthocyanin content, the results indicate that Cabernet Sauvignon of NS–W and Cabernet Gernischt of NS–E can be utilized for an effective strategy. Moreover, the optimal combination planting choices with cultivars would improve wine quality by increasing pigment concentrations linked to the color and antioxidant potential.