Volume 59, Issue No. 1

https://doi.org/10.17113/ftb.59.01.21.6899

Supplement

Impact of Successive Exploitation of a Saccharomyces pastorianus Starter Culture on Saccharide Uptake Dynamics from Wort

Miha Ocvirk¹, Nataša Kočar Mlinarič² and Iztok Jože Košir^1*

¹Slovenian Institute of Hop Research and Brewing, C. Žalskega tabora 2, 3310 Žalec, Slovenia

²Pivovarna Laško Union d.o.o., Pivovarniška ulica 2, 1000 Ljubljana, Slovenia

Article history:

Received: 15 July 2020

Accepted: 26 January 2021

Key words:

beer fermentation, saccharide metabolism, Saccharomyces pastorianus, glucose, fructose, maltose

Summary:

Research background. The production of lager beer includes successive repitchings of a single Saccharomyces pastorianus starter culture. During the beer production process, the yeast is exposed to several stress factors which could affect the fermentation performance. An incomplete fermentation represents a waste of fermentable extract and leads to a beer with higher carbohydrate levels, which could result in a beer with an atypical flavour profile. The aim of the present study is to determine the impact of successive exploitation of a single S. pastorianus starter culture on the wort saccharide uptake dynamics.

Experimental approach. The fermentation was monitored during the production of twelve batches of beer, where the starter yeast culture was reused twelve times without any further treatment. The following beer production steps were monitored: wort production, yeast starter culture propagation, primary fermentation, secondary fermentation and the final product. The work was conducted on an industrial scale employing standard process conditions.

Results and conclusions. Monitoring of the starter culture viability during successive fermentations indicated no reduction in the viability and vitality of the yeast culture. Monitoring of the fermentable wort saccharide concentrations (glucose, fructose, disaccharides and trisaccharides) revealed a correlation between an improvement in saccharide utilisation and starter culture age. Saccharide uptake efficacy proportionally matched the repitching frequency. Successive exploitation of S. pastorianus starter culture has a positive impact on the dynamics of saccharide utilisation from classical hopped wort and the young beer. Furthermore, the final lager beer contains no residues of fermentable saccharides that could affect the overall quality and flavour profile.

Novelty and scientific contribution. Results showed the impact of twelve successive wort fermentations on the dynamics of saccharide uptake that gives brewers important information. The added value of the experiment is all the work done on the industrial scale, with control of all processes and usage of exactly the same raw materials. This study contains usable technological data on the behaviour of saccharides during brewing on the industrial scale, which is not yet found in the literature.

https://doi.org/10.17113/ftb.59.01.21.6695

Sensory and Physicochemical Quality Characteristics of Haddock Fish Cake Enriched with Atlantic Mackerel

Janna Cropotova^1*, Revilija Mozuraityte², Inger Beate Standal², Olga Szulecka³, Tomasz Kulikowski³, Adam Mytlewski³ and Turid Rustad¹

¹Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Sem Saelands vei 6/8, 7491 Trondheim, Norway 

²SINTEF Ocean, Brattorkaia 17C, 7010 Trondheim, Norway

³National Marine Fisheries Research Institute, Kollataja 1, 81-061 Gdynia, Poland

Article history:

Received: 10 March 2020

Accepted: 2 February 2021

Key words:

fish cake, haddock, Atlantic mackerel, sensory attributes, quality parameters, nucleotides, NMR metabolomics

Summary:

Research background. It is desirable to increase the consumption of pelagic fish rich in long-chain omega-3 fatty acids. Partial replacement of traditionally used white fish species by pelagic fish will increase the content of omega-3 fatty acids, and thus improve the nutritional value but it may also affect the consumer acceptance. The aim of this study is to assess the physicochemical and sensory quality of novel fish cake prototypes prepared from haddock and mackerel mince.

Experimental approach. Fillets of haddock and Atlantic mackerel were used as raw material for preparation of fish cakes. The fish fillets were minced, mixed together (in haddock/mackerel mass ratio of 100:0, 75:25 and 50:50) with salt, potato starch, pepper and full fat milk. Physicochemical and sensory analyses were further performed.

Results and conclusions. The fatty acid composition analysis showed that the recommended daily intake of 250 mg of eicosapentaenoic acid and docosahexaenoic acid can easily be reached by consumption of fish cakes enriched with mackerel. The oxidation levels of all fish cakes were low in terms of peroxide value and thiobarbituric acid reactive substance assay (TBARS). Fish cakes prepared with higher mass fraction of mackerel mince (>50 %) had significantly (p<0.05) softer texture than other fish cakes due to higher amount of fat in their formulations. At the same time, these fish cakes were significantly darker than haddock-based (>50 %) fish cakes due to higher myoglobin content in the fish muscle. Moreover, fish cakes with higher amount of mackerel mince had increased yellowness due to the accumulation of water-soluble (r=0.990, p<0.05) and fat-soluble (r=0.976, p<0.05) TBARS. Metabolites relevant for taste and quality were quantified by using ¹H nuclear magnetic resonance (NMR) spectroscopy. The mass fractions of anserine, trimethylamine oxide and β-alanine decreased, while the mass fractions of histidine, glutamic acid and alanine increased with the addition of mackerel. Sensory tests have shown the addition of mackerel did not reduce consumer acceptability of the new fish cakes.

Novelty and scientific contribution. The research demonstrates that Atlantic mackerel can be successfully used for partial replacement of white fish species in fish cake formulations to produce healthy and tasty ready-to-cook products and increase the consumption of small pelagic fish in Europe.

https://doi.org/10.17113/ftb.59.01.21.6820

SARS-CoV2 S Protein Features Potential Estrogen Binding Site

Ante Tomasović^*, Damir Stanzer, Ivan Krešimir Svetec and Marina Svetec Miklenić^*

Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia

Article history:

Received: 27 May 2020

Accepted: 8 February 2021

Key words:

SARS-CoV2, coronavirus, S protein, estrogen, estradiol, estrogen binding site

Summary:

Research background. During the current SARS-CoV2 pandemic, as well as earlier SARS and MERS epidemics, it has been observed that COVID19-positive women on average tend to have milder symptoms and lower fatality rates than men. There is a number of differences between the sexes known to contribute to different immune responses and severity of the disease, one being the effect of estrogen via estrogen receptor signalling. We wondered if estrogen might also affect the SARS-CoV2 more directly, perhaps by binding to the surface glycoprotein (S protein), thus possibly reducing its infectivity.

Experimental approach. To assess whether there is a possibility for estrogen binding on the SARS-CoV2 S protein we used BLAST and HHpred to compare protein sequences of S protein and human estrogen receptor β, while 3D structures of a potential estrogen binding site and an active site of estrogen receptor β were visualized and compared using PyMOL. 

Results and conclusions. By comparing the protein sequence of SARS-CoV2 S protein with the human estrogen receptor β, we identified a potential estrogen binding site on S protein and further determined that it also shares notable similarities with the active site of ER β when observed in 3D structure of their respective proteins. As a control, SARS-CoV2 S protein was compared with the human androgen receptor, and no such similarities were found. The potential estrogen binding site is part of coronavirus S2 superfamily domain, which is involved in host-virus membrane fusion during infection and appears to be conserved throughout the Coronaviridae family.

Novelty and scientific contribution. This preliminary communication shows that SARS-CoV2 S protein features a potential estrogen binding site. Hopefully, this will prompt a more comprehensive study on the possibilities of estrogen binding on the S protein and the effect this might confer on the virus infectivity.