DEVELOPMENT OF PRESERVATION PROCESSES FOR REFRIGERATION-STABLE SEA VEGETABLES: PHYSICOCHEMICAL AND MICROBIAL SAFETY ASPECTS

In recent years, harvesting and farming of seaweeds in US coastal regions, including Maine, has increased rapidly as the economic potential and ecological benefits of farming these crops have been recognized. According to the Maine Aquaculture Impact Report recently published by the Aquaculture Research Institute, Maine's seaweed industry produced ~54,000 pounds of product in 2014 having a farm gate value of over $500,000. A large majority of the farmers who responded to the survey anticipated increasing production by more than 51% by 2020. However, lack of suitable processing infrastructure and knowledge of how to appropriately process harvested sea vegetables into safe, value-added food products have already been identified as significant bottlenecks to the sustainable growth of the sea vegetable industry in the Northeast.

In this study, we investigated the utility of fermentation or dry salting for the production of minimally processed seaweed products with extended shelf life potential. Within processing method, physicochemical characteristics (color, texture) and changes in relevant microbial populations (lactic acid bacteria, aerobic mesophiles, fungi, coliforms) were monitored. We developed a seaweed and cabbage "sauerkraut-style" product and assessed the effects of sea vegetable species (sugar kelp or winged kelp) and seaweed to cabbage ratio (75:25, 50:50, 25:75) on product quality over 60 days of refrigerated storage. We also used dry salting at high (20% and 18% wt/wt) and low (5%, 3% and 2% wt/wt) concentrations to extend the refrigerated shelf life of winged kelp up to 90 days.

Fermentation, as measured by change in pH and population of lactic acid bacteria, was more efficient in samples made with winged kelp compared with sugar kelp samples of the same ratio. Fermented sugar kelp products also yielded lower shear force values than comparative winged kelp formulations, indicating a softer texture. The coliform population in fermented samples appeared to have originated in cabbage and decreased throughout storage in cabbage/winged kelp samples. Cabbage/sugar kelp products did not behave similarly, with the 75% sugar kelp sample showing a net increase in coliform levels during storage. The quality characteristics of dry salted products were maintained well during storage. Salt concentration did not affect significant differences in texture or microbial load. All microbial counts remained < 4 log CFU/g for the duration of the study.

Preliminary results indicate significant promise for the utilization of both fermentation and dry salting to produce value-added products from farmed seaweeds. Additional data in regard to safety in the event of pathogenic contamination as well as consumer liking are needed. These aspects are currently under investigation.