Modified Atmosphere Packaging (MAP) for Seaweed Conservation: Impact on Physicochemical Characteristics and Microbiological Activity

Conventional conservation techniques such as drying, salting or freezing do not allow for preserving the original characteristics of seaweeds. The present work aims to study the impact of minimal processing, in particular "Modified Atmosphere Packaging" (MAP), on the physicochemical characteristics and food safety of two seaweed species, "laver" (Porphyra umbilicalis) and "sea-lettuce" (Ulva lactuca), stored at 6 °C for 15 days. Different parameters were evaluated using analytical methods, namely the composition of headspace gases, color, texture, microorganisms, and volatile organic compounds (VOCs). The main findings of this study were that the MAP treatment was able to inhibit the respiration rate of minimally processed seaweeds, also preserving their color and texture. There was a remarkable reduction in the microbial load for P. umbilicalis treated under modified and vacuum atmospheres, and U. lactuca exhibited relatively steady values with no notable differences between the treatments and the control. Therefore, during the 15-day study period, both seaweeds met the requirements for food safety. GC-TOF-MS allowed to conclude that both MAP and vacuum treatments were more efficient in maintaining the odor characteristics of U. lactuca compared to P. umbilicalis with no significant differences throughout the storage days. Metabolic responses to diverse sources of abiotic stress seemed to account for most of the changes observed.

Antimicrobial activity of Annona muricata leaf oleoresin

Bioactive compounds extracted from plants such as antimicrobials have attracted the attention of consumers and the food industry. This study aimed to determine the antimicrobial activity and chemical composition of Annona muricata leaf oleoresin obtained by supercritical CO₂ extraction. The oleoresin was obtained by supercritical CO₂ extraction and the chemical identification by gas chromatography coupled to mass spectrometry. Antimicrobial activity was evaluated by broth microdilution method against 14 foodborne fungi and bacteria. The oleoresin major chemical class was phytosterols (22.7%) and the major compounds were γ-sitosterol (15.7%), α-tocopherol (13.7%), phytol (13.1%), and hexadecanoic acid (11.5%). Minimum inhibitory concentration against bacteria ranged from 0.0025 to 0.010 mg mL^-1. The oleoresin had high bactericidal activity against all bacteria, mainly Enterobacter cloacae and Pseudomonas aeruginosa with 0.005 mg mL^-1 minimum bactericidal concentration. However, it had low fungicidal activity. The leaf oleoresin of A. muricata has promising applications in food, cosmetic, and pharmaceutical industries.