Quantification of Total Phenols and Antioxidants in Coffee Samples of Different Origins and Evaluation of the Effect of Degree of Roasting on Their Levels

Abstract

Phenolic and antioxidant compounds have received considerable attention due to their beneficial effects on human health. The aim of this study is to determine the content of total phenols and antioxidants in fifty-two coffee samples of different origins, purchased from the Jordanian local market, and investigate the effect of the degree of roasting on the levels of these compounds. The coffee samples were extracted using the hot water extraction method, while Folin–Ciocalteu (FC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay methods were used to analyze these compounds. The results showed that the highest content of total phenol (16.55 mg/g equivalent to GAE) was found in the medium roasted coffee, and the highest content of antioxidants (1.07 mg/g equivalent to TEAC) content was found in the green coffee. Only light and medium roasted coffee showed a significant correlation (p < 0.05, R2 > 0.95) between the average of total phenolic and antioxidant content. A negative correlation between the antioxidant content and the degree of roasting (p < 0.05, R2 > 0.95) were shown, while it did not correlate with phenolic contents. Previously, a positive correlation between antioxidant and chlorogenic acids content was observed, with no correlation between the origin of coffee samples nor heavy metal content, which was previously determined for the same coffee samples. These findings suggest that the antioxidant content for coffee extracts is largely determined by its chlorogenic acid content, rather than the coffee origin or total phenolic and heavy metals content.

Influence of Saccharomyces boulardii inoculation on post‐harvest processing methods on the coffee quality

“…This result was similar to Alnsour et al, 2022, who stated that the caffeine content of roasted beans with different degrees of roasting increased compared with unroasted green beans. Although this study did not conduct different degrees of roasting, the result of increasing caffeine content was similar.…”

“…Although this study did not conduct different degrees of roasting, the result of increasing caffeine content was similar. Literature concluded that the increase in temperature during roasting reduced the water content in coffee beans and released the volatile compound in coffee (Alnsour et al, 2022). Besides, the study indicated that caffeine is considered as a thermostable compound, so roasting did not show degradative effects on caffeine content (Šeremet et al, 2022).…”

“…The concentration of caffeine in coffee beans varies depending on the coffee plant species, geographical origin, storage condition, degree of roasting, etc. (Alnsour et al, 2022;Fuller & Rao, 2017).…”

“…Phenolic compounds are commonly found in fruits and vegetables, chocolates, and beverages including coffee, tea, and cocoa. Literature studied the antioxidant effects of coffee after post-harvest processing to ensure the antioxidant level of coffee, especially for those with different methods of processing (Alnsour et al, 2022).…”

Coffee Origin Determination Based on Analytical and Nondestructive Approaches –A Systematic Literature Review

“…With respect to analytical approaches, several studies used specific chemical compounds such as antioxidant compounds [61], total phenolic compounds, protein, and total lipids [62] as variables for coffee origin classification. However, these studies did not find a significant origin classification when data were modeled with multivariate analysis, as confirmed by Alnsour et al [63].…”