Stability evaluation of gardenia yellow pigment in presence of different phenolic compounds

Highlights

• GYP stability was improved by adding phenols under light and high temperatures.

• FTIR and NMR confirmed that phenols interacted with GYP through hydrogen bonds.

• GYP mixed with phenols possessed high stability under different cooking methods.

Abstract

Gardenia yellow pigment (GYP) may undergo chemical degradation under different conditions resulting in color fading. This study investigated the effects of different phenolic compounds (caffeic acid, rosmarinic acid, tannic acid, epicatechin, chlorogenic acid, epigallocatechin, and epigallocatechin gallate) on the physical and chemical stability of GYP under light and different temperatures. Furthermore, food models with GYP/phenolic compounds were simulated to evaluate the GYP stability under different cooking methods. The addition of phenolic compounds, especially tannic acid, epigallocatechin gallate, epigallocatechin, and rosmarinic acid, significantly improved the GYP stability during light and thermal treatments. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirmed that the formation of hydrogen bonds between GYP and selected phenolic compounds (tannic acid, epigallocatechin gallate, epigallocatechin, and rosmarinic acid), which may lead to the enhancement of GYP stability. Moreover, these selected phenolic compounds provided potent protective effects on GYP under different cooking methods.

Introduction

Color is a crucial parameter for customers to accept products, especially food. Synthetic colorants have been widely applied in the food, textile, and cosmetics industries in the past few centuries. Their usage is mainly attributed to low cost, simplified production, and superior coloring properties. However, the potential health risks of synthetic colorants in food and beverages have raised concerns, including hyperactivity in children and primary biliary cirrhosis in postmenopausal women (Amchova et al., 2015, Bhatt et al., 2018). On the contrary, natural colorants derived from living organisms aroused the interests of consumers in recent years due to their health, environment friendly, and non-toxicity to food. With the growing demand for natural colorants, it is expected that the revenue of natural colorants will reach $ 1620 million by 2023 (Meruvu & dos Santos, 2021).

Gardenia yellow pigment (GYP), a rare water-soluble natural carotenoid, can be extracted from the fruit of Gardenia jasminoides. It has been widely used in beverages, jelly, and noodles due to its excellent water solubility, strong antioxidant activity, and nontoxicity (Wu et al., 2021). Despite these advantages, there are limitations to the commercial application of GYP as natural colorants due to the influence of external environmental factors such as high temperature, light, pH, and oxygen. It has been reported that crocins (the major components of GYP) would degrade and then form volatile compounds such as safranal and other volatile chemicals with 9 or 10 carbons during thermal treatment in the presence of oxygen (Carmona et al., 2006, Gregory et al., 2005, Li et al., 2014). Besides, like other carotenoids, these compounds related to GYP can be accelerated to form the uncolored hydroperoxyl-crocins when exposed to light in an oxygen environment (Manzocco, Kravina, Calligaris, & Nicoli, 2008).

It is crucial to prevent the degradation of GYP and improve its stability during industrial processing and storage. In recent years, it has clearly been shown that phenolic compounds could improve the stability of natural pigments. For examples, the addition of epigallocatechin gallate significantly enhanced the stability of β-carotene during storage at 55 °C (Liu, Gao, McClements, & Decker, 2016). Rosmarinic acid has been found to prevent carotenoid degradation under light treatment (Mesnier, Gregory, Fança-Berthon, Boukobza, & Bily, 2014). The mixtures of carotenoids and phenolic compounds presented strong synergistic interactions, which improved the oxidative stability of the solution system (Jiang et al., 2015). In general, phenolic compounds have strong antioxidant activities due to the existence of the hydroxyl groups. Therefore, the mechanisms involved in stabilizing natural pigments may, in part, be attributed to the fact that phenolic compounds reduce the formation rate of oxidation products through hydrogen atom transfer, single electron transfer, continuous proton loss electron transfer, and transition metal chelation (Zeb, 2020). In addition, phenolic compounds could also improve the stability of pigment by forming non-covalent complexes. As noted in Chuang, Rojanasasithara, Mutilangi, and McClements (2016a), anthocyanins could interact with phenolic compounds through hydrophobic interactions, thus improving the storage stability of anthocyanins. Among these phenolic compounds, caffeic acid, rosmarinic acid, tannic acid, epicatechin, chlorogenic acid, epigallocatechin, and epigallocatechin gallate exhibited significant antioxidants properties, which may improve the chemical stability of GYP and prolong its color stability (Rahimmalek et al., 2020, Singh et al., 2017). Meanwhile, the addition of these phenolic compounds may further expand the application of GYP in the food and beverage industry due to their high nutritional values (Shahidi & Ambigaipalan, 2015).

However, as far as we know, there are no documented detailed investigations on the GYP stability in the presence of phenolic compounds. Traditionally, the stability of natural pigments was evaluated by absorbance measurement. Moreover, CIELAB (L*/a*/b*), an international standard for color measurement, was also widely applied to measure the color differences of food and beverages (Lu & Zheng, 2012). Therefore, this paper aimed to investigate the changes of absorbance and color parameters of GYP in presence of different phenolic compounds (caffeic acid, rosmarinic acid, tannic acid, epicatechin, chlorogenic acid, epigallocatechin, and epigallocatechin gallate) during light and thermal treatments. Then, the possible mechanisms involved in stabilizing GYP were also studied by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Additionally, the thermal stability of GYP containing the presence of selected phenolic compounds in different food models was further evaluated.