Raw and roasted nuts (whether dry- or oil -roasted) are very similar in their nutritional ‘make-up’, but there are some small differences (1-9).

A Nuts for Life audit collected data on the energy and fat content, as listed on the Nutrition Information Panel, of 158 nut products (1). These were sourced from the fresh produce, snacks/impulse, and baking aisles of five Sydney grocery stores, in September 2020.

How does roasting impact nut nutrients?

Energy:

The audit found: The average energy (kilojoule) content is similar between raw (816kJ/30g serve) and roasted nuts (dry-roasted at 779kJ/30g serve, and oil-roasted with 773kJ/30g serve).

Fat:

The audit found: The raw nut products (75 products), with an average of 18g fat/30g serve, had a slightly higher total fat content than the roasted nuts products (66 dry- and oil-roasted products), with a combined average of 15.6g fat/30g serve.

In other Australian data, roasted nuts (specifically, almonds and cashews) are reported as having slightly more total fat (up to 4% more) than raw nuts (2). Research suggests that because nuts are naturally high in healthy fats, they are unable to absorb much additional fat when they are oil-roasted (3).

The USDA Food Composition Database shows very small increases in total fat content, saturated fats, and unsaturated fats (monounsaturated and polyunsaturated), compared with raw nuts. This is likely due to the nutrients in nuts becoming more concentrated as some moisture (water) is lost during the roasting process.  

Nuts are naturally high in healthy fats. This 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.

What about different types of fat?

The audit found: Saturated fat content averaged less than 15% of the total fat, and this was similar for raw nuts and roasted nuts.

A recent study showed that roasting nuts increased the percentage of saturated fat in cashews, almonds and pine nuts, compared to their raw counterparts, but the differences were relatively small (4).  

Some evidence suggests that a negligible amount of trans-fat is produced after roasting nuts, and this depends on the roasting time and temperature. The reported increase in trans-fat is only just measurable, at between 0.07 – 0.9%. 

Table 1: Average fat and energy content of nuts, based on the Nuts for Life audit results (1)

Type of nut Number of products Energy (kJ) per 100g Total fat (g) per 100g Saturated fat (g) per 100g
Raw   75 2,721 60.4 6.7
Oil roasted 38 2,577 51.3 7.3
Dry roasted 28 2,597 52.5 7.6

Minerals

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

Vitamins

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.  

The bottom line

Epidemiological evidence links eating nuts with a reduced risk of chronic disease. These studies typically don’t distinguish between raw or roasted nuts, with study participants likely to have eaten a mixture of both. So, despite some very small nutritional differences between raw and roasted varieties, the many health benefits apply to both!

For more information on the Nuts for Life audit, please contact us at admin@nutsforlife.com.au

References

  1. Nuts for Life. Audit of the salt and fat content of tree nuts. September 2020. Unpublished.
  2. Food Standards Australia New Zealand. Australian Food Composition Database. Available at: https://www.foodstandards.gov.au/science/monitoringnutrients/afcd/Pages/default.aspx
  3. US Department of Agriculture, Agricultural Research Service. USDA Food Composition Database. Available at: https://www.nal.usda.gov/usda-food-composition-database
  4. Ghazzawi, HA., Al-Ismail, K., A comprehensive study on the effect of roasting and frying on fatty acids profiles and antioxidant capacity of almonds, pine, cashew, and pistachio. Journal of Food Quality, 2017.
  5. Alasalvar, C., Pelvan, E., Topal, B., 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.
  6. Amaral, J.S., et al., Effects of roasting on hazelnut lipids. J Agric Food Chem, 2006. 54(4): 1315-21.
  7. Stuetz, W., Schlormann, W., Glei, M., B-vitamins, carotenoids and alpha-/gamma-tocopherol in raw and roasted nuts. Food Chem, 2017. 221: 222-27.
  8. Yaacoub, R., et al., Formation of lipid oxidation and isomerization products during processing of nuts and sesame seeds. J Agric Food Chem, 2008. 56(16): 7082-90.
  9. Schlormann, W., et al., Influence of roasting conditions on health-related compounds in different nuts. Food Chem, 2015. 180: 77-85.
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