The Application of High-Pressure Processing and Green Preservation Media for the Extended Storage of Fresh Hop Cones

Fresh hop cones ( Humulus lupulus L.) are highly perishable and must normally be dried, frozen or immediately used in brewing after harvest to preserve their chemical and aromatic integrity, leading to high energy demand and limited brewing flexibility. This study evaluated the potential of High-Pressure Processing (HPP) combined with green preservation media (+ 0.5% citric acid and + 0.6% acerola extract solutions) as sustainable alternatives to freezing for maintaining hop quality under mild refrigeration. Fresh Cascade hop cones were subjected to 600 MPa for 180 s and stored at 4 °C for up to 60 days. Microbiological stability, colour parameters, α- and β-acid contents, and essential oil composition (GC–MS) were analysed at 15, 30, and 60 days. HPP treatment effectively reduced total viable counts (>3 Log CFU/g) and maintained microbial stability for at least 30 days. Samples preserved in acerola extract or citric acid solution showed significantly slower colour degradation and higher retention of α-acids and myrcene compared to controls in water. After 15–30 days, these treatments maintained chemical and aromatic profiles comparable to fresh hops, whereas marked degradation occurred after 60 days. The combination of HPP with antioxidant and mildly acidic preservation media allowed stable refrigerated storage of fresh hops up to 15–30 days without freezing, representing a novel, energy-efficient preservation strategy for extending the availability of high-aroma hops in brewing and reducing post-harvest losses.