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Nuts & Roasting


How do you roast nuts?

Roasting nuts at home is a simple way to deepen their flavour, making them taste ... nuttier. It also gives them a crisper texture which really makes a difference when adding nuts to salads or desserts.

You can roast nuts with or without oil.

Roasting nuts with oil - it's nice to match the oil with the nut, although it's not essential.
Method:
1. Preheat oven to 180 degrees C
2. Spread nuts in an even layer on a baking tray lined with baking paper. If using oil, use the least amount to coat evenly.
3. Roast for 8-12 minutes, but check every 5 minutes, stirring to ensure they are roasting evenly.
4. When the nuts are browned and smell nutty, remove from the oven and cool on a different plate to ensure they do not continue to brown.

Alternatively, you could coat nuts in egg white by mixing the nuts with egg white in a zip lock bag, then pouring them out on a tray and baking them as above.

Published December 2016

Does roasting or salting affect the Health Star Rating?

Nuts absorb very little of the oil they’re roasted in, and many nuts are dry roasted (see Roasting FAQs), so this has little effect on their star rating. Depending on how much salt is added to the nuts, the salt reduces the star rating by around half to one star.

Last updated July 2016

Are roasted nuts as healthy as raw nuts?

There are five large population studies that link eating nuts with reduced risk of heart disease (1-5). These studies don’t distinguish between raw and roasted nuts and the participants were likely to be eating a mixture of both. The studies found eating a 30g serve of nuts (raw or roasted) at least five times a week can reduce heart disease risk by 30-50%.

There is also no apparent difference in the ability of roasted and raw nuts to lower cholesterol. An almond study found that, as part of a healthy diet, both raw and roasted almonds reduced LDL cholesterol with no change in HDL (6).

Only those nutrients that are not heat stable such as the B group vitamins will be reduced in roasted nuts. However, Australians get most of their B group vitamins from grains and cereals.

References:
1) Albert CM et al. Nut consumption and decreased risk of sudden cardiac death in the Physician’s Health Study. Arch Intern Med 2002;162(12):1382-7.
2) Ellsworth JL et al. Frequent nut intake and risk of death from coronary heart disease and all causes in postmenopausal women: the Iowa Women’s Health Study. Nutrition Metabolism and Cardiovascular Disease 2001;11(6):372-7.
3) Hu FB et al. Frequent nut consumption and risk of coronary heart disease in women: prospective cohort study. British Medical Journal 1998;317(7169):1341-5.
4) Fraser GE et al. A possible protective effect of nut consumption on risk of coronary heart disease. Arch Intern Med 1991; 152: 1416-24.
5) Blomhoff R. et al. Health benefits of nuts: potential role of antioxidants. Brit J Nutr 2007;96(SupplS2):S52-S60.
6) Spiller GA et al. Effects of plant-based diets high in raw or roasted almonds, or roasted almond butter on serum lipoproteins in humans. J Am Coll Nutr 2003;22(3):195-200.

Last Update September 2016

What effects does roasting have on the healthy fats in nuts?

There is evidence to suggest that as long as nuts are roasted at low/middles temperatures (120-160 degrees C), there is no effect on the fatty acid profile(1). However, there is also some evidence that a negligible amount of trans fats are produced after roasting, but this is dependent on the time and temperature of the roast. Despite this, the amount of trans fat is only just measurable between 0.07-0.9% (2-4).

References:
1) Schlormann W. et al. Influence of roasting conditions on health-related compounds in different nuts. Food Chem. 2015 Aug;1(180):77-85.
2) Amaral JS et al. Effects of roasting on hazelnut lipids. J Agric Food Chem. 2006;22;54(4):1315-21.
3) Alasalvar C et al. Effects of roasting on oil and fatty acid composition of Turkish hazelnut varieties (Corylus avellana L.). Int J Food Sci Nutr 2010;61(6):630-42.
4) Yaacoub R et al. Formation of lipid oxidation and isomerization products during processing of nuts and sesame seeds. J Agric Food Chem. 2008 Aug 27;56(16):7082-90.

Last Update September 2016

Is there a difference in the nutrient composition of raw, dry roasted and oil roasted nuts?

Both raw and roasted nuts (whether dry or oil roasted) have a similar nutrient composition, although there are some small differences. Most nutrients – particularly minerals - become slightly more concentrated during the roasting process as nuts lose some moisture. The B group vitamins are not heat stable so their levels are reduced after roasting. However, nuts do not contribute much B group vitamins to the diet so the changes have little nutritional significance. That's because we get most of our B group vitamins from carbohydrate rich foods such as breads and cereals.

Vitamin E can also be reduced by roasting and the amount depends on the nut variety and the length of time being roasted. A light roasted colour is best for both sensory properties and nutrition.

Nuts are naturally high in healthy fats so they are unable to absorb much more fat even if oil roasted. As a result, the total fat of raw and oil roasted nuts varies only by an average of around 5% (based on US nutrition compositional data). While natural (raw) nuts do not contain trans fats, there is some evidence that a negligible amount of trans fats are produced after roasting, but is dependent on the time and temperature of the roast. Despite this, the amount of trans fat is only just measurable between 0.07-0.9% (1-3).

References:
1) Amaral JS et al. Effects of roasting on hazelnut lipids. J Agric Food Chem. 2006;22;54(4):1315-21.
2) Alasalvar C et al. Effects of roasting on oil and fatty acid composition of Turkish hazelnut varieties (Corylus avellana L.). Int J Food Sci Nutr 2010;61(6):630-42.
3) Yaacoub R et al. Formation of lipid oxidation and isomerization products during processing of nuts and sesame seeds. J Agric Food Chem. 2008 Aug 27;56(16):7082-90.
4) Stuetz W, Schlörmann W, Glei M. B-vitamins, carotenoids and α-/γ-tocopherol in raw and roasted nuts. Food Chem. 2017 Apr 15;221:222-227.
5) Schlörmann W, Birringer M, Böhm V et al. Influence of roasting conditions on health-related compounds in different nuts.Food Chem. 2015 Aug 1;180:77-85.

Last Update Jan 2017

How are nuts roasted & in what type of oil?

Roasting intensifies the flavour and the colour of the nut, which people often prefer. Nuts can be roasted both with and without oil.

Roasting without oil: Dry-roasted or Oven-Roasted nuts

Nuts are tumbled around in a machine which is similar to a miniature cement mixer, or in a round cylinder which passes over gas fired burners. The nuts are continuously tossed around to prevent scorching or burning and to give an even distribution of heat.

Dry-roasting can be done at home, either on the stove in a frying pan, tossing or stirring the nuts gently over the heat; or alternatively in a single layer in the oven on a baking tray, stirred from time to time.

Roasting with oil: Oil-Roasted nuts

There are two ways to roast nuts with oil - either Batch Oil roasting, or Continuous roasting. 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. In the case of continuous roasting, the 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.

As nuts are already high in healthy fats, they don't absorb much of the oil they are roasted in (only around 2-5% is absorbed).

Last Update September 2016

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