Peanut (Arachis hypogaea L.) flour and oilcake flour: Exploring the influence of roasting and varietal differences on proximal composition, elemental profiling, antimicrobial and antioxidant properties

Abstract

Peanuts are highly valued for their abundance of essential nutrients and health-promoting phenolic compounds. Peanut press cake, an inexpensive and underutilized agro-industrial by-product of oil production, is typically discarded or used as animal feed. This study investigated the influence of thermal processing and varietal disparities on the nutritional composition, phenolic content, and biological properties of peanut flour and oilcake flour, aiming to enhance their value as food ingredients. The findings showed that roasting significantly increased the oil (9.98 ± 0.11-44.13 ± 0.10 %), ash (1.28 ± 0.01-5.45 ± 0.05 %), carbohydrate contents (0.90 ± 0.01-28.09 ± 0.28 %), and energy value (406.69 ± 0.09-609.13 ± 1.08 kcal/100 g), along with the total polyphenol content (28.64 ± 0.19-62.79 ± 1.18 mg GAE/g), total flavonoid content (4.20 ± 0.07-18.35 ± 0.06 mg QE/g) and antioxidant activity in both peanut flour and its oilcake. Conversely, it led to a reduction in the moisture (1.48 ± 0.09-6.25 ± 0.15 %) and protein content (49.50 ± 0.05-54.24 ± 0.01 %). Notable variations were found between the two peanut varieties in terms of these nutritional parameters. Elemental analysis unveiled significant discrepancies among peanut varieties and with roasting, with potassium (12,237.56 ± 101.36-14,513.34 ± 168.62 mg/kg) emerging as the predominant macro-element followed by phosphorus (6156.86 ± 36.19-8815.22 ± 130.70 mg/kg) and magnesium (3037.92 ± 13.87-4096.44 ± 8.54 mg/kg), while zinc (53.98 ± 0.61-81.77 ± 0.44 mg/kg) predominated among the microelements. Moreover, peanut and oilcake flours demonstrated antibacterial activity against several bacteria. It can be inferred that roasted peanut and oilcake flours offer substantial nutritional value, making them promising candidates for addressing protein-energy malnutrition and serving as valuable ingredients in developing new food products.

Keywords: Biological activity; By-products; Green products; Oilcake flour; Peanut flour; Phenolic content; Sustainable yield.

Graphical abstract

Fig. 1

Principal component analysis describing the relationship among the investigated parameters of peanut flour and peanut cake flour samples. A: Proximate composition (OC, MC, PC, AC, and CC), energy value (EV), and mineral elements (K, Mg, Na, Ca, and P). B: Phenolic compound content (TPC and TFC) and antioxidant activity (DPPH and ABTS). GI: Group I; GII: Group II; and GIII: Group III.

Fig. 2

Dendrogram of the studied peanut flour and oilcake flour varieties analyzed by cluster analysis using Ward's method and Euclidean distance. A: Proximate composition (OC, MC, PC, AC, and CC), energy value (EV), and mineral elements (K, Mg, Na, Ca, and P). B: Phenolic compound content (TPC and TFC) and antioxidant activity (DPPH and ABTS). CI: Cluster I; CII: Cluster II; CIII: Cluster III.