Participation in CONECT 2026: Turning berry press residues into smart packaging

Our team took part in the XIX International Scientific Conference of Environmental and Climate Technologies (CONECT 2026), held from 12–15 May 2026 at the Riga Technical University Auditorium Centre "Domus Auditorialis" in Riga, Latvia. Linards Klavins participated with work from the project under the title "Vaccinium berry press residues as a source of anthocyanins for smart packaging film."

CONECT has been running annually since 2008 and has become one of the region's key gatherings for environmental and climate technology research. Each year it brings together roughly 200 scientists and researchers from more than 25 countries, with a particular emphasis on giving doctoral students and early-career researchers a platform to publish and discuss their results. The 2026 edition centered on the theme of sustainability and resilience, spanning energy systems and environmental engineering. Accepted papers are published in the open-access journal Environmental and Climate Technologies and indexed in Scopus and Web of Science.

When Vaccinium berries are pressed for juice, the leftover residue, skins, seeds, and pulp, is usually discarded, even though it remains rich in anthocyanins and other polyphenols. These natural pigments do more than give berries their deep red and blue colour: they change hue in response to pH and to volatile basic compounds such as ammonia, which are released as food spoils. That makes them promising candidates for biodegradable colourimetric films in intelligent food packaging materials that can give a visible, colour-based freshness signal without any electronics or added sensors.

The study examined press residues from three species blueberry (Vaccinium corymbosum), cranberry (Vaccinium macrocarpon), and bilberry (Vaccinium myrtillus). Anthocyanin-rich extracts were recovered using environmentally friendly methods and characterised by extraction yield and by their total phenolic, anthocyanin, and procyanidin content. Of the three, bilberry residues showed the highest anthocyanin levels, followed by blueberry and then cranberry.

The purified extracts were then incorporated into five biodegradable polymer matrices chitosan, sodium alginate, gelatin, starch, and pectin and cast into films. Each film was assessed for its optical properties, colour stability, pH responsiveness, and sensitivity to the volatile bases linked to spoilage. The key findings:

• All films produced clear, visually distinguishable colour changes across the pH 2–10 range.

• Bilberry-based films showed the strongest colour intensity under acidic conditions and the largest colour change (ΔE) under alkaline conditions.

• Ammonia exposure produced concentration-dependent ΔE responses, with chitosan and alginate films the most sensitive at short exposure times.

By sourcing the active pigment from a juice-industry side-stream rather than from fresh fruit or synthetic dyes, the work ties together two goals at the heart of CONECT: reducing food-processing waste through a circular bioeconomy model, and developing greener, bio-based materials for food packaging.

Smart packaging is part of a broader push to cut food waste and move away from petroleum-based plastics. Sourcing the active ingredient from an agricultural side-stream means the same berries can support both juice production and packaging innovation, getting more value from a single harvest while keeping material out of the waste stream.

We're grateful to the CONECT 2026 organisers and to everyone who stopped by to discuss the work. You can learn more about the conference at conect.rtu.lv.