Writing retreat in Lammi 11.-13.10.2021

The Food Materials Science Research Group, reinforced with Prof. Maija Tenkanen and her Carbohydrate Enzymology and Chemistry Group, spent three days at the Lammi Biological Station of the University of Helsinki.

The classroom was reserved for quiet and calm working, where a good flow was achieved with a number of new articles, grants, and reports developed. Many interactive scientific discussions were held outside of the classroom, whether that be in the sauna, over lunch and dinner, or into the evening. Our team was fed with delicious meals: breakfast, lunch, coffee, and dinners. The food was again wonderful, and we could focus all of our energy on writing and data handling.

We picked mushrooms in the Evo forest area and our master mushroom cook, Hongbo fried these up with plenty of vegan margarine over a live fire as an evening snack. Evening sauna and swimming in the fresh cold water in the Pääjärvi lake was very relaxing. Our trip was most enjoyable, after this heavy covid-closure period, as we readjusted to sitting together and having long evening discussions about science and more with real, living people.

A couple of highlights:

In the writing retreat of 2019, Fabio introduced to the group a modern idea about writing an article together in 24 hours. Unbelievably, the outcome was not quite as easy and fast. Thanks to Fabio’s ongoing dedication to the 24-hour paper, now, after 24 months, we finally celebrated publishing our review article:

Valoppi, F., Agustin, M., Abik, F., Morais de Carvalho, D., Sithole, J., Bhattarai, M., Varis, JJ, Arzami, A., Pulkkinen, EE, & Mikkonen, KS. Insight on current advances in food science and technology for feeding the world population. Frontiers in sustainable food systems.

We got also joyful news from other accepted articles:

Kuribayashi, T., Lankinen, P., Hietala, S., Mikkonen, K.S. Dense and continuous networks of aerial hyphae improve flexibility and shape retention of mycelium composite in the wet state. Composites Part A, accepted.

Hagel, S., Lüssenhop, P., Walk, S., Kirjoranta, S., Ritter, A., Bastidas Jurado, C., Mikkonen, K.S., Tenkanen, M., Körner, I., Saake, B. Valorization of urban street tree pruning residues in biorefineries by steam refining: conversion into fibers, emulsifiers and biogas. Frontiers in Chemistry, accepted.

New analyses to find out the relationship of hemicelluloses to gut health

Investigation of the effect of birch gum on gut health made a giant leap after the university loosened COVID-19 restrictions, and we got back into the lab. We started to develop two different methods for analyzing birch glucuronoxylan. First, we wanted to analyze whether short-chain fatty acid-producing bacteria could utilize birch glucuronoxylan. These short-chain fatty acids produced by gut microbes from some dietary fibers have been found to be beneficial metabolites. They can, for example, protect against colorectal cancer or metabolic syndrome. Although short-chain fatty acids have been investigated in multiple studies, we previously had not measured them from fecal samples. Two methods based on gas chromatography (GC) were tested and modified before we found a protocol that we were happy with.

Birch glucuronoxylan and different diets were analyzed with pyrolysis gas-chromatography mass-spectrometry (pyr-GC/MS). In this way, we could also evaluate the amount and effect of lignin in the diets. The results from both methods have been promising, and we cannot wait for them to be published.

Enzyme industry side stream as a novel source for hydrocolloids

One of the key research topics of our Food Materials Science research group is side stream characterization where we aim to make efficient use of wasted natural resources. In our resent study, we focused on side stream biomass obtained from enzyme industry. This type of biomass is obtained during down-stream processing where the enzymes are separated and collected from the leftover biomass, including for example microorganism cells, and the growth medium. Currently, this biomass is treated as waste. However, the biomass is a source for potentially valuable compounds, for example, cell wall heteropolysaccharides.

Our recently published open access article “Fungal Cell Biomass from Enzyme Industry as a Sustainable Source of Hydrocolloids” by Ida Nikkilä et al. reveals the basic composition of this biomass and the fractions obtained from it via alkaline and water extraction. Further, the functional properties of the extracts as hydrocolloids were studied in water suspensions and emulsions prepared from biomass extracts. The study showed that this type of biomass can be fractioned via water and alkaline extraction, and the extracts have potential as hydrocolloids. More specifically, the alkaline extract was found to form a relatively stable emulsion. This was the first time that fungal biomass was studied as a source for hydrocolloids.

This study was part of the Academy of Finland funded “Reassembly of fungal polysaccharides for biocompatible interfaces” (REPLY) -project. A previously posted blog from this project can be found here.

Links between lignin and hemicelluloses in spruce extract

The Food Materials Science research group continues to innovate in the use of Nordic forest resources in advanced applications for food and other novel materials. For this, a deep understanding on the chemical and structural aspects of wood components is crucial. Assessment of cellulose, hemicelluloses, and lignin alone is needed, but also the identification and elucidation of linkages between those structures: the so-called lignin-carbohydrate complexes (LCCs). Despite of paramount importance for applications, the identification of LCC bonds is challenging because of their relatively low frequency in wood extracts.

A recent research article by Danila Carvalho et al. tackled this challenge and improved the identification of LCC bonds in spruce hot water extract using an elegant combination of fractionation techniques, including chemical, enzymatic, and physical methods. Such techniques resulted in the fractionation of LCC bonds and enabled the identification of three types of LCCs, namely: phenylglycoside (PG), benzylether (BE) and gamma-ester (GE). This research developed an efficient analytical methodology for LCC identification, which may facilitate the study of LCC functionalities and, consequently, open novel opportunities of applications for wood-based derivatives.

This research was a result of the collaborative project: “Role of lignin carbohydrate complexes as key to stable emulsions” (ROCK), funded by Tandem Forest Values programme by Kungliga Skogs- och Lantbruksakademien (KSLA), Sweden, and led by Assist. Prof. Kirsi Mikkonen (University of Helsinki, Finland) and Assoc. Prof. Martin Lawoko (Royal Institute of Technology, Sweden).

The open access article is available here.

New work reveals detailed features of spruce gum (galactoglucomannan) in water

The Food Materials Science group studies the applicability of spruce gum in dispersion-based systems, such as food, beverages, cosmetics, and chemicals. To formulate applications of spruce gum to produce high quality products, knowledge on its solution properties is very essential.

A recently published article by Mamata Bhattarai et al. reveals that spruce gum forms higher-order structures in water, such as aggregates and colloidal particles. We demonstrated this, for the first time, by fractionating and studying all the fractions of spruce gum using asymmetric field-flow fractionation and a combination of light scattering and electron microscopy.

Spruce gum is mainly composed of galactoglucomannan polysaccharides, but also other structures are co-extracted from spruce wood with the polysaccharides. Unpurified spruce gum containing high levels of lignin occurred in water in the form of polysaccharide-aggregate-particle mixture. Spruce gum after purification by ethanol precipitation did not show particles, but the aggregates still existed. Characterization of this unique mixture of spruce gum was challenging; thus, several parameters during the analytical fractionation had to be optimized. The article discusses several aspects about challenges to fractionate complex polysaccharide mixtures and possible approaches to address them.

The work was a result of excellent collaboration between the FoMSci group (Department of Food and Nutrition, University of Helsinki), Department of Physics (University of Helsinki), and the University of Natural Resources and Life Sciences (BOKU), Austria.

The article is available as open access here.

Will future packaging be grown from fungi?

Think about expanded polystyrene and try to imagine something that works like polystyrene, but is much more environmentally friendly, very sustainable, and an economic material.

Fungal mycelia are versatile, highly productive, and sustainable sources for biocomposites to replace conventional plastics. However, only a few fungal strains have been characterized in composites and numerous strains remain unexplored. Many plant residue materials, such as side streams from food production could be used as feeding substrates for mycelia. A research article by Zeynep Tacer-Caba et al. explored this field and studied novel fungal strains, feeding substrates, and dynamic mechanical properties of mycelium composites for the first time at a broad moisture gradient. The research was conducted within the Academy of Finland –funded project Reassembly of fungal polysaccharides for biocompatible interfaces (REPLY). 

The champion of novel mycelium composites, Agaricus bisporus, gave high stiffness and moisture-resistance. The dense structure and rich chemical composition of rapeseed cake made it a potent feeding substrate for mycelia. In this work, the compressive strength of mycelium composites ranged between 17 and 300 kPa. Therefore, mycelium composites may be considered as competitors of expanded polystyrene, as the latter have similar compressive strength (69–400 kPa).

 All tested mycelia composites, either with rapeseed cake or oat husk as feeding substrates, had rather low water uptake at moderate ambient humidity. Therefore, all samples – irrespective of the mycelium and substrate types – seemed to be resilient to moisture. Will future packaging be grown from fungi?

New findings on wood extracts and lignin nanoparticles

A recent research article by Maarit Lahtinen et al. sheds new light on the chemical structures that make wood extracts so efficient in emulsion stabilization. Pressurized hot water extracted hemicelluloses, spruce galactoglucomannans (GGM) and birch glucuronoxylans, contain residual lignin. Some of that lignin may be covalently linked with the hemicellulose structures via lignin carbohydrate complexes. Presence of lignin greatly improves the oxidative stability of emulsions.

Mamata Bhattarai et al. studied how spruce GGM behave in water. GGM show tendency to form physical assemblies during storage, meaning that dissolved hemicelluloses associate with each other and form clusters. This behavior depends on pH, so it is important to take into account when designing future products from GGM.

Alkali-extracted lignin precipitates in acidic pH. Melissa Agustin et al. took advantage of this property and developed lignin nanoparticles, with the help of a rapid ultrasonication treatment. The resulting particles were spherical, negatively charged, and very stable in suspensions and emulsions. The underexploited wood components, hemicelluloses and lignin, have promising properties that could be useful in chemicals, pharmaceuticals, and food.