High-pressure processing technology as a novel approach for improving the shelf-life of fresh hop cones

Aim: Hop cones (Humulus lupulus L.) are essential for the beer flavour, but they deteriorate quickly due to moisture, oxidation, and microbes. Methods like vacuum-nitrogen packaging, cold, and anaerobic storage slowed the degradation of compounds. However, long-term freshness maintenance is difficult and challenging; high-pressure processing (HPP) offers a sustainable way to extend shelf life, and it could enhance the availability without affecting quality. Methods: Fresh Cascade hop cones were submerged in liquids (water (W), 0.5% citric acid (CA) solution, and 0.6% acerola extract (AE)) and treated with HPP at 600 MPa/3 min. Samples were examined for color, oil content, bitter acid, aroma compounds, and microbial growth at 0, 15, 30, and 60 days. Results: At day 0, samples exhibited the highest L* values, which decreased across all liquid treatments after 15 days. By day 30, AE-treated samples had slightly higher all color values than other treatments. W-treated samples significantly dropped a* values at day 60, and CA caused significantly lower b* values across all storage conditions. W-treated samples had a higher browning index at day 60, while the CA-treated sample showed a lower index at day 15 than AE and W, which had similar values. No significant differences were found among the liquid treatments in essential oil yield, however, it was decreased after 15 days of storage compared to day 0. α-acids were higher at day 0 (6.09±0.02%) for all liquid treatments, with a general decline by day 60 (3.58%). W-treated samples showed a significantly lower α-acid at 15, 30, and 60 days. Conversely, AE treatment had higher β-acid at 15 and 30 days. At day 60, CA and W-treatments showed much lower β-acid than AE. Total phenolic content was highest in CA (19.36 mg GAE/g DW) samples at 15 days, and it decreased as storage increased. Although storage time had little effect on bacteria counts, CA-treatment significantly increased microbial growth compared to AE and W-treatments. Conclusion: Microbiologically, samples remained stable for 30 days, except CA. Bitter acids showed minimal change, while HP with acerola extract improved color and aroma. Oil yield, browning, and compound varied with treatment and storage.