A beverage ingredient with a fermentation question

Coffee pulp can become a beverage substrate, but selecting a starter culture changes what that drink tastes like. A study published in August compared four individual bacterial strains and found that Lactiplantibacillus plantarum XJ25 produced the highest overall sensory score under the conditions tested. Its performance also differed from the other cultures in acidity, volatile compounds and chemical antioxidant assays.

The researchers used Arabica coffee harvested in Pu’er, China, in November 2024. They dried the pulp, mixed it with hot water at a 1:100 ratio and added sucrose at 100 grams per litre. After sterilisation, the substrate was fermented separately with Bifidobacterium longum BL11, Lacticaseibacillus casei LC15, Streptococcus thermophilus LB42 or L. plantarum XJ25. An unfermented sample provided the comparison.

The same substrate, different results

Fermentation ran for 48 hours at 37 °C, with intermediate sampling to follow acidity, sugars and viable cell counts. The experiment was repeated three times, but samples came from the same batch. That design helps compare starter behaviour within a controlled substrate; it does not establish how different harvests or industrial batches would behave.

The plantarum treatment ended at pH 4.42, compared with an initial 4.62, and retained the highest viable count at 48 hours. The researchers also reported a 59.48% decline in its reducing sugars. They explicitly distinguish that measurement from the sucrose added to the formulation: the percentage concerns endogenous reducing sugars, principally glucose and fructose. It therefore cannot support a claim that the finished drink contains 59.48% less total sugar.

Aroma instruments and a small tasting panel

Two analytical methods, GC-MS and GC-IMS, examined the volatile profile. In the GC-MS comparison, total measured volatile concentration reached 901.92 micrograms per litre in the plantarum sample, against 383.54 in the control. Esters were particularly prominent, and fermentation produced distinct profiles rather than one uniform improvement across every chemical class.

Twelve trained assessors evaluated the drinks. The plantarum sample had the highest overall score, with favourable assessments of taste and flavour persistence. Colour ratings, however, declined after fermentation. These results identify a promising formulation direction within a small trained panel; they do not establish broad consumer preference or acceptance in a particular retail market.

What the functional measurements can support

Chemical tests also found stronger antioxidant activity after fermentation. For the plantarum treatment, DPPH radical-scavenging activity was 54.72%, compared with 26.22% in the control, while ABTS results were 64.06% and 42.18%, respectively. These are assay results from the beverage, not measurements of a health effect in people. The study supplies no basis for a disease-prevention claim.

For product developers, the useful result is the comparison between named strains in a defined coffee-pulp formulation. L. plantarum XJ25 merits further investigation, but the authors still call for mixed-culture studies and optimisation of fermentation parameters. Shelf-life performance, production consistency and the finished drink’s nutritional profile remain separate questions from the laboratory flavour and antioxidant findings.

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