Effects of Packaging and Storage Condition on the Physicochemical and Microbial Properties of Whole and Powdered Gracilaria tenuistipitata

Abstract

Gracilaria tenuistipitata is a widely utilized edible seaweed. This study evaluated the effects of packaging conditions (open, sealed and vacuum) and storage duration (up to 9 months) on the physicochemical and microbial quality of sun-dried whole seaweed and oven-dried powder (60 °C for 7–8 hours). Proximate composition, antioxidant capacity and phytochemicals (flavonoids and anthocyanins) were measured by AOAC, DPPH and colorimetric methods, while functional groups, sensory attributes and microbial quality were evaluated using FTIR, hedonic scale and selective media for total plate count and pathogens. Results showed that moisture reached 15.9% in whole and 8.62% in powdered seaweed. Protein declined to 19.31% in whole and 20.28% in powdered samples, while fiber, lipid and ash also decreased. Vacuum packed powder retained the highest quality with 4.17% moisture, 22.19% protein and 41.79% ash, whereas vacuum packed whole seaweed showed faster nutrient loss (11.08% moisture, 22.7% protein and 37.3% ash). Sealed packaging provided moderate protection. Antioxidant capacity decreased most (p < 0.05) in open packed whole seaweed (3.63 mg TE/100 g) and least in vacuum packed powder (4.31 mg TE/100 g). Vacuum packed powder preserved 82.5% of flavonoids and 139.76 mg TA/100 g anthocyanin. pH and water activity increased in open packs, indicating potential microbial growth. FTIR spectra detected degradation-related functional groups such as alkanes, aromatics and amino acids in open packed samples. Functional properties of powder, including water holding capacity (5.57 g/g, 5.36 g/g) and oil holding capacity (1.41 g/g, 1.25 g/g), remained higher under vacuum and sealed packaging, respectively. Sensory evaluation showed vacuum packed whole and powdered seaweed-maintained acceptability scores above 5, while open-packed samples dropped below 4 at 9 months. All samples were initially free from E. coli, Salmonella, Shigella and Vibrio cholerae. Total plate counts were lowest in vacuum packed powder (4 × 10² CFU/g) and reached unacceptable levels in open-packed whole seaweed (5.67 × 10⁵ CFU/g) at 9 months. In conclusion, vacuum packaging demonstrated the best preservation up to 9 months. Powdered seaweed showed higher stability than whole seaweed despite lower initial nutritional values, while sealed packaging was moderately effective for up to 6 months. These results will support the commercial potential of G. tenuistipitata as a stable, value added food product under optimized packaging conditions.