# Impact of Lactic Acid Bacteria on Immunoreactivity of Oat Beers
## 4 Conclusions  
Summing up the results of the experiments, it can be stated that despite the high risk of oat contamination with other cereals, oats show a much lower immunoreactivity than barley, although the immune response to oat proteins is strongly dependent on individual sensitivity.  
The application of a starter culture of lactic acid bacteria with steeping water did not result in the expected attenuation of the immune response at the malting stage to a statistically significant extent. However, in the course of the beer production process, most of the proteins causing the immune reaction were removed, mainly during the production of wort. The remaining immunoreactivity was further reduced in subsequent technological stages. The residual immune reaction in oat beer is caused by a protein fraction with a molecular weight of 38-40 kDa.  
The process of simulated digestion in vitro resulted in a further weakening of the immune response. The residual immunoreactivity in oat beer obtained from sour malt was significantly lower than that for barley beers. This indicates the degradation of toxic peptides as a result of the hydrolytic activity of lactic acid bacteria and the beneficial effect of lactic fermentation on the reduction of the immunoreactivity of the oat raw material. The analysis performed with human sera showed a very diverse response of celiac disease patients to oat products. However, despite the high probability of oat contamination with other cereals and the very diverse human sensitivity to gluten, the remaining immunoreactivity in digested oat beers did not exceed 2.0%, which suggests their good tolerance by celiac. So far, there are no reference values defining the acceptable level of residual immunoreactivity, but it can be assumed that oat beer is safe. First, the remaining immune response indicates the presence of only trace amounts of the original level of gluten contamination. Moreover, unlike bread, beer is consumed occasionally, and its dry matter content is much lower, so the potential dose of unintentionally consumed gluten will not exceed the acceptable threshold.  
However, in order to increase the efficiency of gluten cleavage, it is necessary to carefully select LAB starter cultures for the production of sour malt. The search should be focused on strains with the greatest potential to degrade complex secondary structures of gluten, which are resistant to hydrolysis by enzymes in the gastrointestinal tract, and to degrade toxic amino acid sequences.  
At the same time, the conducted studies clearly indicate that in the search for solutions ensuring 100% dietary safety of oat beers for people with high gluten sensitivity, a strategy of hurdle technology should be adopted, based on the simultaneous use of several procedures with potentially synergistic effects. In addition to the already mentioned use of sour malts with effectively reduced immunoreactivity, it seems reasonable to optimize the mashing process aimed at further hydrolysis of toxic sequences, which can also be supported by using exogenous enzyme preparations.  
**Author Contributions:** Conceptualization, A.D. and E.K.-B.; methodology, A.D., E.K.-B. and J.L.; formal analysis, P.P.; investigation, A.D., P.P., E.K.-B. and J.L.; writing--original draft, A.D. and P.P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The research was funded by The Ministry of Science and Higher Education in Poland, grant number N N312 359539.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.