Unveiling the Nutritional Profile and Safety of Coffee Pulp as a First Step in Its Valorization Strategy

Abstract

The coffee pulp, a significant by-product of coffee processing, is often discarded but has potential for recycling and high-value uses. This study aimed to investigate the chemical composition of two coffee pulp ingredients, a flour (CPF) and an aqueous extract (CPE), and conducted acute and sub-chronic toxicity assays to determine their safety. The proximate composition revealed the high fiber content of both ingredients; the CPF mainly contained insoluble fiber, while CPE consisted exclusively of soluble pectic polysaccharides. The CPF had higher concentrations of amino acids and a better balance of essential/non-essential amino acids, whereas the CPE exhibited higher concentrations of free amino acids, ensuring higher bioavailability. Both ingredients showed elevated mineral content, while heavy-metal concentrations remained within acceptable limits. This study established the bioactive potential of the CPF and the CPE, demonstrating the high content of caffeine and gallic, protocatechuic, and 4-caffeoylquinic acids. The toxicity studies revealed that the CPF and the CPE exhibited safety when orally administered to mice. Administered doses were non-toxic, as they did not induce lethality or adverse effects in the mice or produce significant histopathological or biochemical adverse changes. This study represents a first step in valorizing the CPF and the CPE as safe novel food ingredients with health benefits for functional and nutritional foods.

Keywords: (poly)phenols; amino acids; bioactive compounds; caffeine; coffee pulp; dietary fiber; food ingredient; minerals; safety; toxicity.

Figure 1

Assessment of protein quality in coffee pulp flour (CPF) and coffee pulp extract (CPE) based on essential amino acid (EAA) composition and derived parameters, including the concentrations of individual EAAs (mg AA g−1 protein) (A), where black horizontal lines indicate the amino acid scoring pattern (mg AA g⁻¹ protein) of the reference protein (WHO/FAO/UNU Expert Consultation, 2007), the amino acid scores (AAS), expressed as the percentage of each EAA in the sample relative to its content in the reference protein (B), the concentration of total EAA (TEAA), total conditionally EAA (TCEA), total aromatic AA (TAraA), total sulfur AA (TSAA), total branched-chain AA (BCAA), and specific grouped AA and (mg AA g⁻¹ protein) (C), the Fischer, Lys/Arg, predicted protein efficiency (p-PER) ratios (D), the predicted nutritional index (p-NI) and biological value (p-BV) for CPF and CPE (E). Data are presented as means ± SD. Asterisks (*) indicate significant differences (p < 0.05) between CPF and CPE according to T-test.

Figure 2

Effects of acute oral administration of coffee pulp flour (CSF) or coffee pulp extract CPE) on body weight, organ weight, and histology in mice, including body weight and weight gain in male (A,B) and female (C,D) mice after a 14-day acute toxicity test with 2000 mg kg⁻¹ CPF or CPE. Relative organ weights of the heart, liver, kidney, thymus, and spleen of male (E) and female (F) mice collected 14 days after the acute toxicity test with a dose of 2000 mg kg⁻¹. Representative histological images of liver, kidney, and intestine from control and treated (CPF or CPE) male and female mice (G). Data are presented as means ± SD. Asterisks (*) indicate significant differences (p < 0.05) compared to the control group when subject to the Dunnet test.

Figure 3

Effects of sub-chronic oral administration of coffee pulp flour (CPF) or coffee pulp extract (CPE) on body weight, organ weight, histology, and biochemical parameters in female mice, including body weight (A), weight gain (B), and in the evolution of body weight (C) in female mice during the 90-day sub-chronic toxicity test with a dose of 1000 mg kg⁻¹. Relative organ weights in female mice, including heart, liver, kidney, thymus, and spleen, obtained after the sub-chronic toxicity test with a dose of 1000 mg/kg (D). Representative histological images of liver, kidney, and intestine from control and treated (CPF or CPE) female mice (E). Serum levels of total cholesterol (F), LDL cholesterol (G), HDL cholesterol (H), triglycerides (I), insulin (J), and leptin (K) after the sub-chronic toxicity test. Data are presented as means ± SD. Asterisks (*) indicate significant differences (p < 0.05) compared to the control group when subject to the Dunnet test.