Kelp as food ingredient : processing and product evaluation
Doctoral thesis

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2024Metadata
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- Doctoral theses (KBM) [136]
Abstract
Developing a more sustainable food production system calls for innovations, including increased use of underutilized resources and introduction of novel ingredients in food. Cultivation of seaweed is environmentally friendly since it requires few input factors such as freshwater and fertilizers while it at the same time assimilates nutrients from the surroundings and sequester carbon. The resulting raw materials can make important contributions to future foods with nutrients, flavour and texture. For most Western consumers, seaweeds are rare ingredient, and the number of food products is low. Triggering market demand requires increased development of seaweed-containing food products. In Norway, there is a growing seaweed industry focused on cultivation of two kelp species: Saccharina latissima (sugar kelp) and Alaria esculenta (winged kelp). Large-scale use of these seaweeds in food products require further development of processing and preservation methods that produce safe, nutritious and flavourful raw materials as well as more knowledge on how the incorporation affect food product properties. The objective of this thesis was twofold: first, to examine the impact of post-harvest processing and preservation methods on the overall quality of cultivated kelp; second, to explore its direct use in food applications and the development of functional ingredients.
High iodine content in kelps is one of the main challenges for a wider use of brown seaweeds in frequently consumed food products. In Paper 1 it was shown that by employing freshwater and seawater treatments the iodine content in sugar kelp could be reduced with 73 and 59 %, respectively. Descriptive sensory analysis showed that using seawater resulted in more salty and intense flavour compared to using freshwater. It was also found that inclusion of dried seawater-treated kelp at amounts that kept iodine levels below the upper recommended intake levels, significantly altered the flavour of a commercial product.
Preservation of sugar kelp by addition of acidic seawater containing lactic or citric acid was demonstrated in Paper 2. A final pH between 3.7-4.1 was reached allowing for storage at ambient temperature for at least 56 days (8 weeks). In general, acid concentration affected the extent of biomass loss and changes in composition. Apart from reducing iodine and total arsenic contents, acid preservation also resulted in lower cadmium content. Sensory profiles were also significantly affected by acid type and concentration, mainly in terms of saltines and sourness. Overall, the results showed that choice of processing and preservation conditions influences the nutritional and sensory properties of sugar kelp.
The high mineral content of seaweeds provides a salty taste making them attractive as a salt replacer. Moreover, consumer studies have revealed positive attitudes towards the use of seaweed in foods like bread. In Paper 3, it was found that the use of varying levels of unfermented and fermented sugar kelp or winged kelp as partial salt replacers had significant impact on technological dough properties and the resulting breads. The addition of kelp resulted in equal salty flavour as a full-salt control, but it also provided breads with seaweed flavour and odour. Fermented sugar kelp was found to be the most promising candidate for partial salt replacement in bread due to providing a more desirable sensory profile. Furthermore, in Paper 4, a process for producing crude alginate-rich products from kelp capable of forming gels was developed. It was hypothesized that such ingredients have the potential to replace commonly used texture-enhancing ingredients and meet the increasing demand for so-called “clean-label” ingredients. Plant-based meat analogues is a product category where use of clean-label ingredients could increase consumer acceptance and the developed ingredients were therefore tested as binders in patties based on texturized soy protein. This resulted in patties with robust structural integrity but with soft instrumental texture that was notably different from a commercial plant-based burger analogue. Further work would be needed to optimize the ingredients and formulations to provide an adequate replacement for currently used texture-ingredients.
Altogether, the findings in this thesis can provide useful knowledge for further development of the seaweed value chains to produce kelp ingredients for food applications as well as their use in future food products. For å utvikle et mer bærekraftig matproduksjonssystem kreves det innovasjoner, blant annet økt bruk av underutnyttede ressurser og introduksjon av nye ingredienser i maten. Dyrking av tang og tare er klimavennlig siden det ikke krever innsatsfaktorer som ferskvann og kunstgjødsel, samtidig som det tas opp CO2 og næringsstoffer fra omgivelsene. Råvarene som blir produsert, kan gi viktige bidrag til fremtidens matvarer i form av næringsstoffer, smak og konsistens. For de fleste forbrukere i den vestlige verden er tang og tare en sjelden ingrediens som bare finnes i et fåtall matprodukter. For å øke etterspørselen i markedet kreves det utvikling av nye matprodukter som inneholder tang og tare. I Norge er det i dag en fremvoksende tare-industri basert på dyrking av to tarearter: Saccharina latissima (sukkertare) og Alaria esculenta (butare). Storskala bruk av disse tareartene i matvarer krever videreutvikling av prosesserings- og konserveringsmetoder for å sikre trygge, næringsrike og smakfulle råvarer, samt mer kunnskap om hvordan inkorporering av tare påvirker matproduktenes egenskaper. Målet med denne avhandlingen var todelt: for det første å undersøke hvordan prosesserings- og konserveringsmetoder etter innhøsting påvirker den generelle kvaliteten på dyrket tare, og for det andre å både utforske direkte bruk av tare i næringsmidler og utvikle funksjonelle ingredienser.