by Kristin Neumann

An apple a day ...

With every apple we ingest a huge community of bacteria.
With every apple we ingest a huge community of bacteria.

Apples are among the most commonly eaten fruits in the world.

The apple is one of the most important sources of >>> flavonoids in our diet and it contributes significantly to our health with apple >>> procyanidins and >>> pectin. But not only that! With every apple we ingest a huge community of bacteria. So far no one investigated the bacteria which colonize an apple in detail and is there a difference between organic apples and conventionally-treated apples? >>> Gabriele Berg and her colleagues from the University of Graz (Austria) took a closer look at the apple.

Berg and coworkers have taken the apple (Malus pumila, Paradise Apple) apart and examined stem, fruit pulp, peel and seeds individually. In total, they have found approximately 100,000,000 (100 million) bacteria per gram of apple. Each part of the apple harbored different types of bacteria. Surprisingly, most bacteria were found in the pulp and in the seeds, the peel was less heavily colonized. If we eat only the peel and pulp of an apple, we consume about 40 million bacteria with the organic apple and about 10 times less with the conventional apple.

It was interesting that most of the bacteria were found in the apple seeds, the type of bacteria was very similar to those in the pulp. Seems like the apple microbiome is inherited directly to the offspring.

Rather organic than conventional?

The number of bacteria was similar in both organic and conventional apples, but there were found significant differences in bacterial diversity. The organic apple was much more diverse than the conventional apple. In the organic apple, the pulp showed the highest bacterial diversity, the conventional apple had the highest bacterial diversity in the peel, although the organic apple had a greater bacterial diversity on each part of the apple.

In all apples Proteobacteria dominated with 80%, followed by Bacteroidetes with 9%, Actinobacteria (5%) and Firmicutes (3%). On conventionally grown apples, there were found significantly more Enterobacteriales- a group of bacteria that include those that can cause food-borne outbreaks - than on organic apples.

Organic apples were colonized by more bacteria, which are also good for our health i. e. Lactobacillus species, than conventionally treated apples. The high bacterial diversity of organic apples ensures that bacteria that are pathogenic to humans have no chance to propagate on the apple.

This study once again shows that untreated foods are significantly better for our health than treated ones. Not only the unhealthy treatment itself, but also the consequences for the processes inside the apple through the treatment, impair the benefits for our health. So rather pick the apple from the neighbor's apple tree than buy it from the supermarket! Of course, ask in advance :-)

Dr. Kristin Neumann
Dr. Kristin Neumann

I was always curious about how life works in its tiny details and ended up spending a lot of time in the lab, working with these bacteria and getting a PhD in Microbiology. I always had the idealistic idea of working on something that changes peoples live for the better …

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