Antioxidant and antibacterial activities of Thai culinary herb and spice extracts, and application in pork meatballs.
Twenty-two local Thai culinary herbs and spices normally used for cooking were screened for their antioxidant properties by using FRAP, DPPH and TBARS assays. Four ethanolic extracts, i.e., holy basil, Vietnamese coriander, turmeric and green peppercorn, having high antioxidant properties were selected for freeze-drying and used in the pork meatball batter. The batter of pork meatball was prepared with 0.2% (w/w) freeze-dried ethanolic extract of each selected herb and spice. The meatball model was obtained by cooking the batter stuffed in plastic casing and cut into 2.5 cm per piece. The meatballs were aerobically and vacuum packaged and stored at 4°C for 9 days. Antioxidant and antimicrobial efficacies of the extracts in the meatball samples were performed every 3 days. It was found that holy basil, Vietnamese coriander and green peppercorn showed stronger antioxidant effect in the pork meatballs than did turmeric throughout 9 days of storage period in both aerobic and vacuum conditions (p<0.05). Regarding the standard for the marginal acceptable microbial counts of ≤ 5.0 log cfu/g sample, holy basil and green peppercorn extracts provided up to 9 days shelf life for the meatballs packaged in both aerobic and vacuum conditions while those made with Vietnamese coriander and turmeric extracts had the shelf life of about 6-9 days and control meatballs had shelf life less than 6 days.