Influence of preservation methods on biochemical composition and downstream processing of cultivated Saccharina latissima biomass

Eva Albers,Eric Malmhäll-Bah,Joakim Olsson,Martin Sterner,Joshua J Mayers,Göran M Nylund,Katarina Rupar-Gadd,Mehdi Abdollahi,Suzana Cvijetinovic,Ulrika Welander,Ulrica Edlund,Henrik Pavia,Ingrid Undeland

doi:10.1016/j.algal.2021.102261

Abstract

Saccharina latissima biomass cultivated along the Swedish west coast was subjected to four different scalable preservation methods after harvest; freezing, sun-drying, oven-drying and ensiling. Freeze-drying and freezing at −80 °C were also included to provide dry and wet references. The effects of the different preservation methods on the composition of Saccharina biomass (on dry weight, DW, basis), and the recovery as well as properties of high-quality protein, alginate and biogas were evaluated. Sun-drying significantly reduced protein, alginate and fatty acid content of the seaweeds and thereby concentrated ash in the biomass compared to the other methods. Protein/amino acids and fatty acids were significantly concentrated in ensiled biomass, while mannitol and laminarin were reduced compared to the other biomasses. Oven-drying and −20 °C freezing affected the composition the least, with lower ash content and alterations in some specific amino and fatty acids. Sun-drying and ensiling resulted in significantly lower protein solubility at high pH compared to the other biomasses which translated into the lowest total seaweed protein recovery using the pH-shift process. Highest protein yield was obtained with the freeze-dried reference. Ensiling lead to a significant decrease in the molecular weight of alginate, while sun-drying caused a negative effect on alginate by inducing a shift in the guluronic and mannuronic acids composition of alginate. Sun-drying gave the lowest methane yield in the anaerobic digestion experiments while freezing at −80 °C gave the highest yield, closely followed by freezing at −20 °C and ensiling. To conclude, preservation methods must be carefully chosen to protect the valuable component in Saccharina latissima, and to achieve an efficient downstream processing ultimately yielding high quality products as part of a seaweed biorefinery.

Highlights

Cultivated seaweeds have gained interest as a potential source of biomass in the conversion from a fossil-dependent to a biobased society
The results show ensiling of S. latissima to be a potentially efficient method of preservation when the biomass will be used for anaerobic digestion
Chemical composition of cultivated S. latissima biomasses was greatly affected by the preservation methods, where sun-drying reduced the content of several compounds compared to the other preservation methods

Summary

Introduction

Cultivated seaweeds have gained interest as a potential source of biomass in the conversion from a fossil-dependent to a biobased society Further to their high contents of hydrocolloids, seaweeds have been increasingly addressed as a potential source of food protein not competing with other crops for arable land. Heat-aided drying is a very common method for stabilization of fresh plant-like organisms like seaweeds, especially in the preparation of certain frac tions like ulvan and lipids [3,5]. It results in a faster drying rate but requires high amounts of energy. It has been shown that oven-drying leads to higher protein extractability and in vitro protein digestibility while freeze-drying results in proteins with better physicochemical properties [1]

Objectives

Methods

Results

Conclusion