Nuts are grown and processed in many ways, and depending on the method, their nutritional value may differ slightly. We summarise the various nut processing methods.

Organic

The link between organic food consumption and health remains inconclusive [1]. There is some research suggesting that organic foods contain more vitamin C and phosphorous [2], and a higher content of phenolic compounds [1]. However, in general there’s a lack of evidence that organic foods, including nuts, are significantly more nutritious.

Pasteurisation 

Pasteurisation is a process that kills microbes (mainly bacteria) in food and drink, such as milk, juice and canned foods. It’s widely used in food manufacturing as a proven method to help achieve food preservation and food safety.

To minimise bacteria, some nuts may also be pasteurised, using either heat, or heat and steam, to surface treat the product. And in fact roasting is a recognised way of pasteurising nuts. Research shows that pasteurisation techniques do not affect the nutritional value of nuts or their sensory qualities (like taste and crunch).

Activation (soaking)

Activated nuts are soaked in water (usually overnight). Proponents of activated nuts believe that this breaks down some of the proteins, starches, oils and other nutrients like phytates, making them more digestible.

There is some evidence that soaking grains and legumes reduces phytates, but there is little evidence for this in nuts. In fact, research has found no evidence that activating nuts makes their nutrients more bioavailable to the body. And phytates themselves have antioxidant capabilities, so reducing them is not necessarily beneficial.

If you enjoy activated nuts, continue to eat them. If you’re happy to eat regular raw or roasted (non-activated) nuts, you will still get all the health benefits.

Ground nuts (including nut butters/pastes)

Ground nuts provide many of the benefits of whole nuts. For instance, pure nut butters – those without added oil, sugar, salt, or other flavours – are full of protein, fibre, and all the nutrients found in whole nuts.

Nuts can also be ground and milled into a course flour. Nut ‘meals’ still contain the nutrients of the whole nuts, although the fibre content can be reduced if the nuts are blanched before milling.

The main difference is that grinding (and finely chopping) nuts breaks down their fibrous structure, releasing some of the fat that is ‘trapped’ in the fibrous structure of the whole nut. This means that more fat is available to be absorbed by the body.

This doesn’t mean you need to avoid them, as ground nuts, including nut butters, are an excellent option for infants and younger children, who are at risk of choking on whole nuts, and the older people or those with chewing difficulties. 

Blanched nuts

Blanched nuts are temporarily soaked in hot water to soften the seed coats for removal. This reduces the fibre content, as the coat is a good source of fibre and is also thought to have a prebiotic effect. Blanched nuts are often used in cooking or for decoration.

Roasting nuts

Whether dry or oil roasted, the nutrient content of roasted nuts varies only slightly compared to raw natural nuts.

Most nutrients, particularly minerals, become more concentrated during the roasting process, as moisture (water) is lost. As a result, roasted nuts have less water and a slightly higher concentration of minerals.

B-group vitamins and vitamin E are not heat stable. This means their levels are slightly reduced in roasted nuts, compared with raw nuts, due to the roasting process. The amount of loss depends on the nut variety and the length of roasting time.

Roasting can also cause the nut skins (which contain fibre and antioxidants) to fall off, meaning less of these nut components in the end product.

Nuts can be roasted with or without oil.

Oil-roasted nuts

There are two ways to roast nuts with oil:

Batch oil roasting – is where nuts are placed in a stainless-steel basket and cooked in hot oil in a machine (similar to a chip fryer). 

Continuous roasting – in which nuts travel through the roasters continuously, via a mesh conveyor system.

The Australian nut industry uses both methods using the same type of oil as the nut (for example macadamias are roasted in macadamia oil). However, sometimes other unsaturated oils are used – such as peanut, sunflower or canola. The oils are tested for quality before use, and the type of oil is chosen to maximise the freshness and shelf life of the nuts.

Did you know? Nuts roasted in oil have only slightly more total fat (up to 4% more) than raw nuts. This is because nuts are naturally high in healthy fats, which means that, even when oil-roasted, they are unable to absorb much more fat. So the fat content is similar between raw and roasted nuts.

Dry or oven-roasted nuts

Commercially, dry-roasting nuts involves tumbling them around in a machine, which is similar to a miniature cement mixer, or in a round cylinder, which passes over gas-fired burners. Continually tossing around the nuts prevents scorching or burning, and gives them an even distribution of heat.

Dry-roasting can be also done at home, either on the stove in a fry pan, tossing or stirring the nuts gently over the heat, or alternatively, by placing them in a single layer in the oven on a baking tray, and stirring them from time to time.

Nut milks

Plant-based beverages have grown in popularity in recent years. These include those made from grains (such as oats and rice), legumes (like soy) and nuts (including almonds and macadamias). It’s important to keep in mind that the actual level of nuts in these milks is small – only 2-10%. This means that, in making nut milks, some of the nutrients naturally found in whole nuts are left behind in the fibrous “pulp”.

If you make nut milks at home, be sure to use the “pulp” as an ingredient in cooking, rather than discarding it. If you are buying commercial plant-based beverages, make sure they are fortified with calcium – to a level of around 120mg per 100mL.

If you enjoy nut milks continue to use them, but bear in mind that nutritionally, they are not a substitute for a handful of nuts a day.

Nut storage

Storage length and location can impact the nutrients in many foods, including nuts. The longer nuts are stored in higher temperatures and humidity, the more likely their fats are to turn rancid.

For this reason, nuts are best stored in air-tight containers (to reduce oxygen levels and keep moisture out), in the fridge or freezer. They can be kept nuts in the fridge for up to 4 months, or the freezer for up to 6 months.

Bring nuts back to room temperature, or warm slightly in the microwave, before eating them to bring back the volatile oils that give nuts their delicious nutty taste.