Extracting and stabilising natural food colourant from spruce and pine needles - a new publication!

Logging in the boreal and hemiboreal forests of northern Europe generates large volumes of spruce and pine residue each year, much of which remains unused. Conifer needles within this residue are a rich source of chlorophyll, the pigment responsible for the green colour of plants and a compound of growing interest to the food industry as a natural alternative to synthetic dyes.

A study by Alise Zommere and Linards Klavins at the National Centre of Forest and Water Research (University of Latvia), published in Scientific Reports, addresses a practical question: whether this chlorophyll can be recovered efficiently, stabilised, and incorporated into food products. The findings indicate that it can, provided appropriate extraction, encapsulation, and storage conditions are met.

Synthetic food dyes are inexpensive and stable, but several, including certain azo and triphenylmethane dyes, have been associated with health concerns and environmental persistence. Regulatory pressure and consumer demand are driving a shift toward natural pigments. Chlorophyll is a strong candidate. In addition to its colouring properties, chlorophyll and its derivatives exhibit antioxidant and antimicrobial activity and have been investigated in the context of cancer prevention and therapy. Conifer needles are a particularly suitable source because they are abundant, renewable, and currently discarded, meaning their use supports both waste valorisation and the broader objectives of a circular bioeconomy. The principal challenge is stability. Chlorophyll is sensitive to heat, light, oxygen, and acidity, so efficient extraction alone is insufficient. The pigment must also be protected once incorporated into a food matrix.

The study compared two conifer species, Norway spruce (Picea abies) and Scots pine (Pinus sylvestris), across fresh and dried needles, a range of solvents, and three extraction techniques: ultrasound-assisted extraction (UAE), maceration, and Soxhlet extraction. Several consistent patterns emerged. Fresh spruce needles yielded the highest chlorophyll-a content, approximately 0.31 g per 100 g of dry weight, compared with 0.24 g for pine, consistent with the higher native pigment content of spruce. Fresh needles outperformed dried needles for both species, as drying degraded the pigment; the authors note, however, that dried biomass offers advantages in storage and handling, a trade-off that may be addressed through gentler drying methods. Among the extraction techniques, UAE achieved comparable yields to the alternatives while requiring only 30 minutes, compared with 24 hours for maceration and approximately 3 hours for Soxhlet extraction, with lower energy use and reduced exposure to the prolonged heat that can degrade pigments. Acetone was identified as the most effective solvent, its intermediate polarity interacting well with both regions of the chlorophyll molecule. Notably, maximum chlorophyll recovery and maximum total extraction yield occurred under different solvent conditions, indicating that higher overall extract does not equate to higher pigment content. Optimisation using response surface methodology identified the biomass-to-solvent ratio as the dominant factor, with excessive sample loading reducing efficiency. The most favourable pigment recovery was obtained with a low sample load and a longer extraction time, with ultrasound intensity kept low for energy efficiency, as it had little effect on the outcome.

To evaluate stability in a real product, the extracted chlorophyll was encapsulated in two food-grade carriers, maltodextrin and inulin, and incorporated into plain yoghurt, an acidic, moisture-rich environment in which chlorophyll is typically unstable. Storage temperature was the decisive factor in colour retention. Under refrigeration at 4 °C, the coloured yoghurts retained their colour well over the six-day test period. At 21 °C, colour loss was pronounced, with analysis confirming near-complete conversion of chlorophyll to pheophytin, its degraded form. The two carriers performed similarly, suggesting comparable physical protection under the tested conditions. An inclusion rate of approximately 3% produced a clearly visible, saturated green; higher rates did not meaningfully improve colour and increased degradation-related colour shifts at room temperature. These results indicate that encapsulation renders chlorophyll compatible with acidic dairy products but does not remove the need for appropriate cold storage.

Significance

The study establishes ultrasound-assisted extraction with acetone as an efficient method for recovering chlorophyll from conifer needles and demonstrates a viable route from forestry residue to a functional food colourant. Further work is required, including sensory evaluation, consumer acceptance, and bioavailability studies, as well as enhanced stabilisation strategies such as co-encapsulation with antioxidants. Nonetheless, the study demonstrates a clear direction: the conversion of a low-value forestry side-stream into a high-value, food-compatible natural pigment, contributing to more sustainable products within a circular economy framework.

Read more --> Zommere, A. & Klavins, L. (2026). "Optimised extraction and encapsulation-based stabilisation of chlorophyll from conifer needles for use as a food colourant." Scientific Reports. https://doi.org/10.1038/s41598-026-65534-0. Published open access under a Creative Commons Attribution 4.0 International License.