Changes in some Physical and Chemical Properties of Black Mulberry (Morus nigra L.) Concentrate during Storage

Abstract

The current study investigated changes in color parameters, 5-hydroxymethylfurfural (HMF), total monomeric anthocyanin (TMA) and total phenolic content (TPC), phenolic profile, antioxidant, and antimicrobial activities of black mulberry concentrate produced from dried black mulberry fruit at the beginning (day 0), on days 20, 40, and 60 during 60-day storage at two temperatures ( $20\pm 2^{°}\text{C}$ and $4\pm 2^{°}\text{C}$ ). It was revealed that black mulberry concentrate was a rich source in terms of TPC (550.06 μg GAE/mg) and antioxidant activity (IC50) (ABTS, 8.03 μg/ml; DPPH, 10.38 μg/ml) at the beginning of storage. At the same time storage time had a significant ( $p<0.01$ ) effect on HMF, $a^{\ast }$ , $b^{\ast }$ , $C^{\ast }$ , $H^{°}$ , TPC, DPPH, and ABTS, storage temperature had a significant ( $p<0.01$ ) effect on HMF, TMA, and DPPH. It was found that the HMF content increased during storage, and this increase was higher at room temperature. During storage, a decrease was recorded in $a^{\ast }$ , $b^{\ast }$ , $C^{\ast }$ , and $H^{°}$ values. TPC increased during storage, and this increase was higher at refrigerator temperature. TMA was determined to increase significantly at refrigerator temperature. While DPPH antioxidant activity decreased during storage, antioxidant activity determined by ABTS increased. Chlorogenic acid and kaempferol-3-glucoside were identified in black mulberry concentrate, and it was revealed that the amounts of these compounds decreased during storage at both storage temperatures. It was determined that the dried black mulberry concentrate did not exhibit antimicrobial activity against the microorganisms tested in the study.