Evaluation of heavy metals and phytochemical composition of commercial and homemade Lebanese pomegranate molasses

Abstract

Pomegranate (Punica granatum L.) is one of the oldest known edible fruits that grow in the Mediterranean region, Southeast Asia, and Himalayas .Pomegranate is believed to have a high antioxidant activity because of its richness in active secondary metabolites such as phenolic acids, tannins and flavonoids, including anthocyanins, flavanols, and flavonols. Pomegranate molasses is a traditional condiment that can be obtained by boiling of pomegranate juice without the further addition of sugar or other additives. It is commonly used to improve the taste and aroma characteristics of salads and various dishes in different cultures. Pomegranate molasses is sold either as a commercial processed product, with a variety of brands, or as a traditional homemade product. In our study we evaluated and compared the phytochemical composition of all brands of commercial Lebanese pomegranate molasses; in addition to some homemade samples. The mean TPC in commercial samples was found to be lower than that in homemade samples (25.55 ± 14.22 mg GAE/g, 37.27 ± 10.78 mg GAE/g respectively, p value = 0.126). The mean TFC in commercial samples was also found to be lower than that in homemade samples (75.29 ± 61.9 mg QE/g, 124.21 ± 24.68 mg QE/g respectively, with p value = 0.141 > 0.05). Alkaloids were not detected in any of the samples. The mean TT in commercial samples was found to be lower than that in homemade samples (53.67 ± 23.09 mg TA/g, 104.31 ± 47.59 mg TA/g respectively, with p value = 0.001 < 0.05). Lead and Cadmium were not detected by AAS in any of the samples. Homemade samples were found to be more concentrated than the commercial samples in arsenic (0.197 ±0.13 mg/kg) > 0.1571 ± 0.063 mg/kg) chromium (7.96 ± 2.74 mg/kg > 5.51 ± 3.69 mg/kg), and copper (0.902 ± 1.09 mg/kg > 0.35 ± 0.54 mg/kg). All samples were found to have similar mercury content (0.005 mg/kg). Only 1 homemade sample and 5 commercial pomegranate molasses samples tested in our study showed comply with arsenic Codex (ML) maximum limit of 0.1mg/kg ; however, the other 3 homemade samples and the 23 commercial samples showed to have an arsenic concentration exceeding 0.1mg/kg. On the other hand, all the samples were found to comply with the ML of Cd and Pb respectively (0.05 mg/Kg; 0.1 mg/Kg). 14 commercial and 1 homemade sample were shown to have copper concentration less than the maximum allowable limit reported by GSO (0.21 mg/Kg), while the other 3 homemade samples and the 14 commercial samples showed to have copper concentrations greater than 0.21 mg/Kg with a maximum of 2.46 mg/Kg. All the tested pomegranate samples were found to have Cr concentrations exceeding the maximum allowable limit in fresh vegetables defined by the Food Safety Standards in China (0.5 mg/Kg) with a mean of 5.817 ± 3.646 mg/Kg. The overall results showed that the difference between the Total phenolic content (TPC), Total flavonoid content (TFC), and heavy metal composition in commercial and homemade samples was not statistically significant. Only total tannins (TT) showed a significant difference between the two groups. This could be due to the difference of pomegranate fruit, soil, climate, extraction, processing techniques, and the types of additives used.