HSI Hops (Hop) Storage Index Analysis

Hop storage index, known as HSI for short, is used to estimate alpha-acid and beta-acid losses during storage and processing.

The main uses of hop storage index analysis are:

• Evaluation of various differences in storage
• Measuring permeability and antioxidant levels in lupulin glands
• Determining hop rates in breweries
• Evaluation of grower and dealer processing practices

The levels of certain compounds in hops change as hops age, mishandled, or not stored properly. Acids tend to decrease over time, while degrading compounds associated with oxidation increase. During the spectrophotometric analysis of hops, acids and degrading compounds can be detected as they absorb light of different wavelengths. Hops acids absorb light at 325 nm, and oxidation-related disintegrating compounds absorb light around 275 nm.

The degradation of hops coincides with a gradual increase in the absorbance ratio of the hop extract at these wavelengths of light. The hop storage index (HSI) is calculated by dividing the absorption of hop extract at two different wavelengths. Therefore, HSI increases as hop quality deteriorates. HSI depends on the variety and can change from year to year.

The hop storage index is a useful indicator of hop quality for growers and brewers. Measuring this index at harvest and after processing before use provides brewers with information on hops freshness. Studies show that the higher the index at harvest, the greater the deterioration in storage.

Generally, HSI levels below 0.30 are an indication of good quality hops. The evaluation is as follows:

• Good quality if HSI is less than 0.30
• Acceptable quality if HSI is between 0.30 - 0.40 but lower the better
• Questionable quality if HSI is greater than 0.40

Harvest timing, temperature, oxygen, and storage time all affect the hops storage index. Quality control is therefore essential during harvesting, drying, baling, processing, packaging and storage. Hops should be pelleted as soon as possible after harvest and stored frozen in vacuum, oxygen-free bags. HSI remains stable even after 24 months when hops are properly handled and stored.

Our organization also provides HSI, hop storage index analysis services with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.