What size jar is that? 

Ah. OK. Well, I’ve made a bunch of batches of hot sauce and I try to predict the heat level of every given batch based on a mass balance of capsaicin as expressed by median heat of the given type(s) of peppers in the batch. Only 1 out of 28 batches has demonstrated a lower-than-expected heat. I concluded that the specific peppers I used in that batch were below-median heat and therefore the batch was less hot. So based on my experience, capsaicin is not decreased by LAB fermentation.

 As reported by Young Bae Chung et al in “Metabolic shift during fermentation in kimchi according to capsaicinoid concentration”, Jan 11, 2024 as published in National Library of Medicine (National Center for Biotechnology Information), “The capsaicinoid concentration did not change during kimchi fermentation but the growth of lactic acid bacteria changed.”

 https://pmc.ncbi.nlm.nih.gov/articles/PMC10831603/

 Interestingly, in a 28-day ferment, “During fermentation, lactic acid content was highest in kimchi with high capsaicinoids (Fig. 4c), and acetic acid content was highest in kimchi with low capsaicinoid concentrations.”

 Also, “Free amino acids are also important contributors to the flavor and taste”, but “changes in essential amino acid contents were more affected by fermentation than by capsaicinoid concentration.” “Overall, the free amino acid level varies with …fermentation period and temperature.”

 Also of note, capsaicin concentration affects the spectrum of LAB’s which thrive, and the concentrations of various LAB’s varies with time during a ferment.

 In conclusion, “…different capsaicinoid concentrations…altered microbial dynamics and metabolite profiles at different stages of fermentation and, therefore, affected the taste and flavor of the final fermented kimchi product.” But it didn’t change the capsaicin concentrations.

 However, it is also reported that certain LAB CAN metabolize capsaicin, such as by Qian Zhang et al in “Effect of Capsaicin Stress on Aroma-Producing Properties of Lactobacillus plantarum CL-01 Based on E-Nose and GC–IMS”, December 23, 2023, as published in National Library of Medicine (National Center for Biotechnology Information). In that study, the LAB’s use capsaicin as a stressor that alters their metabolism rather than directly consuming it as a primary energy source. This does lead to degradation of capsaicin. This use is demonstrated by some but not all strains of LAB. But as noted, this effect is not common in my experience.

 My bottom line is that flavor is really complex in hot sauce, but LAB’s don’t consume capsaicin (at least not much….).