Improvement of Naturally Derived Food Colorant Performance with Efficient Pyranoanthocyanin Formation from Sambucus nigra Anthocyanins Using Caffeic Acid and Heat.

Consumers and regulations encourage the use of naturally derived food colorants. Anthocyanins (ACN), plant pigments, are unstable in foods. In aged red wines, ACN with a free hydroxyl group at C-5 condenses to form pyranoanthocyanins (PACN), which are more stable but form inefficiently. This study attempted to produce PACN efficiently using high cofactor concentration and heat. Elderberry anthocyanins were semi-purified and caffeic acid (CA) was dissolved in 15% ethanol and diluted with a buffer to achieve ACN:CA molar ratios of 1:50, 1:100, 1:150, and 1:200, then incubated at 65 °C for 5 days. The effect of temperature was tested using ACN samples incubated with or without CA at 25 °C, 50 °C, and 75 °C for 7 days. Compositional changes were monitored using uHPLC-PDA-MS/MS. Higher CA levels seemed to protect pigment integrity, with ACN:CA 1:150 ratio showing the highest tinctorial strength after 48 h. PACN content growth was fastest between 24 and 48 h for all ACN:CA ratios and after 120 h, all ACN had degraded or converted to PACN. PACN formed faster at higher temperatures, reaching ~90% PACN in 24 h and ~100% PACN in 48 h at 75 °C. These results suggest that PACN can form efficiently from elderberry ACN and CA if heated to produce more stable pigments.

Red pepper (Capsicum annuum) carotenoids as a source of natural food colors: analysis and stability-a review.

Carotenoids are increasingly drawing the attention of researchers as a major natural food color due to their inherent nutritional characteristics and the implicated possible role in prevention and protection against degenerative diseases. In this report, we review the role of red pepper as a source for natural carotenoids. The composition of the carotenoids in red pepper and the application of different methodologies for their analysis were discussed in this report. The stability of red pepper carotenoids during post-harvest processing and storage is also reviewed. This review highlights the potential of red pepper carotenoids as a source of natural food colors and also discusses the need for a standardized approach for the analysis and reporting of composition of carotenoids in plant products and designing model systems for stability studies.

Optimization and characterization of chestnut shell pigment extract obtained microwave assisted extraction by response surface methodology.

The objective of this study is to find optimum conditions to valorize chestnut shell bioactive compounds with coloring pigments through microwave-assisted extraction. With this aim, response surface methodology with central composite design was used. Microwave power (800 W), extraction time (12 min) and solvent concentration (NaOH: 0.115 mol/L) were determined as the optimum conditions to maximize the responses like color value, total phenolic content and total antioxidant capacity. In the optimized extract (OE), characterization of brown melanin like pigments were assessed by Spectrophotometer, Fourier Transform Infrared Spectrometer and major phenolics were identified as; gallic acid, ellagic acid, protocatechuic acid, catechin, and epicatechin as 0.53, 0.48, 0.46, 0.46, 0.14 mg/g dried weight (dw) by High Performance Liquid Chromatography, respectively. In terms of antibacterial activity, OE inhibited the growth of Staphylococcus aureus. Consequently, chestnut shells were successfully processed into natural coloring agents that were possessing strong brown color properties as well as high bioactive potential.

Effect of tannins on microwave-assisted extractability and color properties of sorghum 3-deoxyanthocyanins.

Sorghum derived 3-deoxyanthocyanins (3-DXA) are of growing interest as natural food colors due to their unique stability compared to anthocyanins, but are generally difficult to extract. Microwave-assisted extraction (MAE) can dramatically improve extraction efficiency of 3-DXA from sorghum tissue. However, condensed tannins common in some sorghums could impact MAE extractability and color properties of 3-DXA. The objective of this work was to determine how presence of condensed tannins affect MAE extractability, stability, and color properties of sorghum 3-DXA. Sorghums of varying 3-DXA profile and tannin content, as well as purified tannins, were subjected to MAE and pigment yield and profile, aqueous color properties and stability at pH 1 - 5 monitored over time using, UV-vis spectroscopy, colorimetry, and UPLC-MS. The relative yield of 3-DXA from tannin sorghums was higher (3 - 10-fold) after MAE than from non-tannin sorghum (2-fold). During MAE, condensed tannins underwent extensive oxidative depolymerization to anthocyanidins (cyanidin and 7-O-methylcyanidin), which caused the tannin-sorghum pigment extracts to have a redder hue (12-43H°) compared to the non-tannin pigment extract (58H°). The tannin-derived anthocyanidins transformed over time into xanthylium pigments, resulting in increased extract H°. Tannins enhanced both color intensity (pH 1) and stability (pH 3-5) of the 3-DXA over 14 days, indicating they acted as copigments. The presence of tannins in sorghum enhances MAE extractability of 3-DXA from sorghum tissue, and could also potentially enhance their functionality in aqueous food systems. However, the initial changes in extract hue properties due to tannin-derived anthocyanidins should be considered.