What You Need to Know
During fermentation, naturally occurring lactic acid bacteria such as Lactobacillus plantarum metabolize the high fructose content of guava into lactic acid, reducing the pH from about 5.5 to 3.5–4.0. The acidification not only preserves the jam but also imparts a mild tartness that balances the fruit’s sweetness. The process is temperature‑sensitive, requiring 25–30 °C to favor bacterial activity while suppressing spoilage yeasts.
The Science
Primary Reaction
Fermentation of fructose to lactic acid by Lactobacillus plantarum (lactic acid fermentation).