Comparative Analysis of Commercial and Homemade Grape Pekmez: Antioxidant Contents and HMF Levels

Abstract

Grape pekmez (molasses) is one of the most traditional food products consumed in Azerbaijan, Türkiye and the Middle East, especially in regions where viticulture is widespread. The present study compared the levels of total phenolics (TPC), flavonoid contents (TFC), antioxidant activities, and 5-hydroxymethyl furaldehyde (HMF) contents in grape pekmez samples, both commercially produced (n = 5) and homemade (n = 19). Although TPC, TFC, and antioxidant activity were similar in both types of pekmez, homemade samples had notably higher HMF content (242.24 mg L^-1) compared to the legal limits of 75mg L^-1 in Turkish Food Codex and 40 mg kg^-1 in non-heat treated honey as per Codex Alimentarius. Commercial samples had a significantly lower average HMF content (26.24 mg L^-1) compared to homemade pekmez because, in industrial production, water evaporation is carried out under vacuum, unlike homemade pekmez, which is prepared under uncontrolled atmospheric pressure. Additionally, approximately 74% of the homemade samples had total soluble solid contents (°Brix) below the codex minimum requirement of 68%. In commercial production, water evaporation is usually carried out at about 60°C under vacuum, whereas in homemade production, it occurs at around 100°C under atmospheric pressure. Homemade samples exhibited an HMF content nearly ten times higher than commercial samples (p < 0.05). Pearson’s correlation test indicated a positive and significant correlation between TPC and DPPH values (R = 0.738, p < 0.01). Principal component analysis (PCA) indicated that commercial pekmez production is more effective in preserving grape antioxidative components and minimizing HMF content compared to homemade production. In summary, producing grape pekmez under vacuum conditions ensures better quality by lowering HMF levels and adhering to regulatory standards.