Lesson 8 - Brewing with Hops

How do we select hops? Traditionally, hops were hand selected by the brewer on a visit to the grower or trader. Nowadays, with hops sometimes purchased from farms on the other side of the globe, this is impractical. In such instances, samples of dried hops delivered to the brewery can be examined. However, most hops are selected by variety and laboratory analyses.

Although we usually rely on laboratory analysis, it is also important to know what to look for when carrying out a physical examination.  

Regardless of variety, hops should ideally:

• Be free of pests and diseases.
• Have a good appearance (colour, texture, uniformity, wholeness of cones).
• Have an aroma that is characteristic of the variety with no cheesy or chemical notes.

If the hop looks and smells bad, it is unlikely to perform well in the brewery and may contribute off-flavours to beer.

When evaluating a hop sample, we first assess the physical appearance and then the aroma.

Key things to evaluate:

• Colour – this should be typical for the variety, but generally green in colour. Check for discolouration such as red, brown or black colouring. Brown may indicate oxidation or windburn. Rust colouring may be due to late picking. Black colouring may be due to mould.
• Lupulin – to gauge the amount of lupulin present, split the cone in half longitudinally. Big, fat yellow glands generally indicate high α-acid varieties, while small, thin glands suggest low α-acid hops. A deep orange colour may suggest oxidation or too much heat from the kiln.
• Mould – sooty black mould may be indicative of an aphid infestation, or due to poor storage.
• Cone damage – the cones should be whole (within reason).
• Moisture – does the hop shatter in your hand? Overly dry hops can become brittle. Ideally, we want the lupulin to give an oily feel when the hops are rubbed between your palms.
• Size – are there any abnormally sized cones? If so, this may be due to powdery mildew damage.
• Pests/Disease – check for any signs of pest or disease damage:
  • Red discolouration – may be due to spider mite.
  • Black discolouration –may be mould due to aphids.
  • Silver/brown spots – mildew.
• Seeds and leaf-stems – there should be very few leaf-stems and no seeds in the sample.

Next, in order to get a sense of natural aroma, sniff the hops without rubbing them.  Cheesy/musty notes indicate poor storage; burnt notes suggest excessive drying.

Now rub some hops between your hands, bringing your hands to your nose to get the aroma from the lupulin. Rubbing ruptures the lupulin glands and releases the essential oils, offering an indication of the hops’ aroma e.g. citrus, fruity, spicy or floral. Garlic and onion aromas are undesirable, and may indicate that the hops are over-mature and beginning to oxidise.

The aroma derived from the brewing process is almost never the same as what we smell when we rub hops. Dry hops added after fermentation gives an aroma closest to this but even then, the beer’s background aroma influences what we smell. Most of the essential oils from hops added early in the process are lost and those that survive are in different proportions to those in the oil of the raw hop and may have been changed by biotransformation.

If we don’t get the opportunity to evaluate whole hops we should evaluate pellets.

• Pellets should be green (shade of green depends on variety) in colour – brown may indicate oxidation. A glassy appearance is a sign of excess heat during processing.
• The pellet should break apart easily when rubbed between your fingers.
• The aroma should be a fresh hop aroma – a cheesy aroma suggests oxidation.

Some brewers make hop tea with pellets or whole cone hops and hot water to evaluate aroma (and if you are either very brave or a masochist) taste. 

For other hop products, we can check that the colour and aroma are as we would expect.

With all types of hop product we are not trying to diagnose a problem, we are deciding if the hop is suitable for our beer. Setting a specification using acceptable and unacceptable photographs and an aroma profile helps us to do this more consistently. If the hops don’t look and smell as we specify, we must not purchase/use them!