Thermal stability of some flavonoids and phenolic acids in sheep tallow olein

Abstract

In this study, the thermal stability of some phenolic antioxidants including flavonoids (quercetin and catechin) and phenolic acids (gallic acid, tannic acid, ellagic acid and caffeic acid) in tallow olein was investigated. Tallow olein fractionated from sheep tallow fat was used as a medium to study the antioxidant activity at 120, 140, 160 and 180°C. In order to extract tallow olein, a three‐stage fractionation method was performed on sheep tallow fat at the constant temperatures of 25, 15 and 5°C using acetone as a solvent. The results suggested that quercetin and ellagic acid had the highest thermal stability amongst others, while gallic acid and caffeic acid exhibited the least thermal stability.Practical applications: The sheep tallow fat has been primarily used in soap manufacturing and its application as an edible fat has been limited due to its high content of saturated fatty acids. Extraction of the liquid phase of tallow fat (tallow olein) by fractionation reduces its long‐chain saturated fatty acid content to an acceptable level for edible consumption. The fractionation process, as negatively affects the stability to autoxidation, should be followed by stabilisation with antioxidants. The recent interest in natural antioxidants encouraged the authors to investigate the thermal stability of phenolic antioxidants in tallow olein. It is necessary to determine the thermal stability of antioxidants to predict their appropriateness to be used in high‐temperature applications such as deep frying. Fractionation and stabilisation with appropriate antioxidants are the important steps to utilise tallow olein as an edible oil for different applications in salad formulations, cooking and frying.

Wheat-water chestnut flour blends: effect of baking on antioxidant properties of cookies

“…Thus, it can be suggested that an improved retention of antioxidant activity in water chestnut at higher temperatures can be due to hydroxylation of quercetin (B-ring). Elhamirad and Zamanipoor (2012) gave similar explanation for thermal stability of flavonoids in sheep tallow olien frying. Better retention of antioxidant activity due to hydroxylation of flavonoids is indirectly favored by the fact that WC flour has greater percentage of flavonoids than wheat flour.…”

“…One of the major flavonoids present in WCF was quercetin (Chiang et al 2008). Elhamirad and Zamanipoor (2012) have reported Quercetin to have higher values of standard coefficient (Q s ), a measure of antioxidant activity at higher temperatures (140, 160, 180°C). Thus, it can be suggested that an improved retention of antioxidant activity in water chestnut at higher temperatures can be due to hydroxylation of quercetin (B-ring).…”

Unraveling the mechanism of thermal and thermo-oxidative degradation of tannic acid

“…Thermal degradation behavior of condensed tannin extracted from Radiata pine bark is reported in literature [9]. In their work, Gaugler and Grigsby suggest that condensed tannin extracted from Radiata pine is stable for processing at temperatures below 200 C. However there are very few reports on the thermal degradation of hydrolysable tannin [1,[10][11][12]. Considering the fact that hydrolysable tannin is a processable type of tannin, the study of its thermal stability and thermal degradation behavior is important from an application standpoint.…”

Comparisons on enhancing the immunity of fresh and dry Cordyceps militaris in vivo and in vitro

“…Drying changes the chemical constituents and bioactivities of Chinese traditional medicine (Chen et al, 2004). Some drying processed products are considered to have lower active value than their respective fresh commodities mainly due to the loss of activity compounds, such as polysaccharide, total polyphenol (TP) and total flavonoids (TF), etc during processing (Ginzberg et al, 2008;Katsube et al, 2009;Elhamirad and Zamanipoor, 2012). On the other hand, certain compounds have been observed to increase in different spices after drying, for example, eugenol in bay leaf (Díaz-Maroto et al, 2000), thymol in thyme (Venskutonis, 1997).…”