Almond skin in sourdough bread: nutrition and hygiene
What it found
Adding powdered almond skin to sourdough bread increased its antioxidant capacity and changed its colour, aroma and texture.
In lab tests, the bread also carried some unwanted bacteria and bacterial spores.
What they found
Animal and lab studies
Hygiene and bacteria
Almond skin powder contained Enterobacteriaceae and coliforms. Doughs with almond skin also had these bacteria and Bacillus, and the baked breads had low levels of aerobic bacterial spores (about 2.0 Log CFU/g).
Antioxidant protection in cells
In human intestinal-like cells, the digested fraction from 5% almond skin bread reduced oxidative stress by about 50%, and the 10% bread completely prevented it.
Other findings
Antioxidant capacity
Bread with 5% or 10% almond skin had 1.5 and 1.8 times more antioxidant capacity before digestion. After simulated digestion, the 10% bread released almost 100% of its phytochemicals.
Colour and texture
Almond skin made crust and crumb darker, reduced the air pockets in the crumb, and increased firmness. The 10% bread lost less water during baking than the control.
Aroma compounds
Breads with almond skin had more terpenoids like limonene and β-pinene, and fewer alcohols and aromatic hydrocarbons. The odour intensity increased but bread odour diminished.
What the authors conclude
“Besides the positive functional properties of PAS, this work also evidenced the hygienic issues of almond skin and, in order to avoid potential risks for the human health, highlighted the need to preserve its microbiological characteristics during storage for their reuse in bread production.”
Also in their conclusions
- They say that almond skin improved the functional properties of the bread but also highlighted hygiene issues.
- They advise that the microbiological characteristics of almond skin must be preserved during storage to avoid potential risks for human health when reusing it in bread production.
How it was done
Almond production creates large amounts of by-products rich in polyphenols. The authors wanted to test almond skin as a food ingredient to functionalize a traditional sourdough bread.
They made sourdough bread with 5% or 10% powdered almond skin replacing semolina, plus a control without almond skin. They measured the bread's acidity, microbes, colour, texture, aroma, antioxidant capacity and how it behaved in simulated digestion and in human intestinal-like cells.
What it can’t tell you
- This study was done in the lab and in cells, not in people, so it cannot show what happens when people eat the bread.
- The bread was tested in a simulated digestion and in human intestinal-like cells, not in a real human gut.
- The long-term health effects of eating bread with almond skin are not known from this work.
Who paid
- Conflicts
- Declaration of competing interest The authors declare that there is no conflict of interest for this research.
- Authors work at
- Università degli Studi di Palermo, Italy; Research and Innovation Centre, Italy; University of Palermo, Italy
The paper
- Title
- Reuse of almond by-products: Functionalization of traditional semolina sourdough bread with almond skin
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Gaglio R, Tesoriere L, Maggio A, et al (2023). Reuse of almond by-products: Functionalization of traditional semolina sourdough bread with almond skin. International journal of food microbiology. doi:10.1016/j.ijfoodmicro.2023.110194Free full textPubMed 37004495DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error