Nuts And Almonds: Better Raw Or Roasted?

Should you eat nuts and almonds raw or roasted? Do they lose vitamins when roasting? Or are there even pollutants? How can roasting change nuts and almonds?

Are Roasted Nuts Healthy?

Nuts are wonderfully nutritious and filling foods. They are suitable as snacks or as a basis for plant-based drinks, dips, crackers, or plant-based cheese.

Nuts are packed with healthy fats, fiber, and proteins, and they also provide vitamins, minerals, trace elements, and antioxidants.

Below we discuss

• whether roasted nuts are healthy,
• whether there is a loss of vital substances during roasting,
• whether harmful substances can also form during roasting and
• whether it is better to eat raw nuts.

If you don’t have time to read the whole article, below you will find a summary of all information as well as all-important tips for healthy nut consumption.

How do the calorie and nutrient content change during roasting?

When roasting, the nuts are heated dry, i.e. without the addition of oils, fats, or water, so that they take on a brownish color on all sides.

During the roasting process, the nut initially loses some liquid, which is why the fat and calorie content increases, but only slightly, so that the difference between raw and roasted nuts is hardly relevant.

How does the fat of the nuts change when they are roasted?

The unsaturated fats, which are considered heart-healthy and cholesterol-lowering, become more susceptible to damage and/or oxidation when roasted. Harmful free radicals can form, which in turn can cause cell damage.

However, the change in fatty acids can be prevented by a well-controlled roasting process. The temperature should be low to medium, so not too high. On the other hand, the higher the temperature and the longer the roasting process, the more oxidation of the fatty acids occurs.

For example, if walnuts are roasted at 180 degrees Celsius for 20 minutes, the levels of malondialdehyde (a substance believed to be an indicator of fatty acid oxidation) increase 17-fold. Malondialdehyde levels increase only 1.8-fold in hazelnuts and 2.5-fold in pistachios under similar conditions.

The reason for these differences is that walnuts contain over 40g of polyunsaturated fatty acids (linoleic acid, alpha-linolenic acid) per 100g, while hazelnuts have just 6g and pistachios just over 7g.

However, if the walnuts are roasted for 25 minutes at medium temperatures (120 to 160 degrees Celsius), the extent of fat oxidation is far less. So if you roast nuts in the kitchen for just a few minutes at a medium temperature, you can almost rule out any negative effects on the fatty acids they contain.

However, roasted nuts do not keep as long as raw nuts. Roasting changes the structure of the nut so that the polyunsaturated fatty acids it contains are no longer so well protected and have become even more sensitive to oxidation processes during storage so that the nut goes rancid faster.

Can roasting produce trans fats?

Roasting processes can also produce trans fats (18), with 0.6 to 0.9 g of trans fats per 100 g of nuts. The limit is 2 g of trans fatty acids per 100 g of food, so roasted nuts would be even lower here.

Trans fats can promote calcification of the blood vessels and increase the risk of dementia, diabetes, and obesity.

Are antioxidants lost during roasting?

Nuts are excellent sources of vital substances as they contain many vitamins, minerals, trace elements, and antioxidants. However, since some vital substances are sensitive to heat, it can be assumed that some of the vitamins and/or antioxidants contained are lost during roasting.

Substances with an antioxidant effect, which protect the body against free radicals and thus protect against cell damage, are often broken down or inactivated under the influence of heat. However, this does not apply to all antioxidant substances. As with vitamins, there are substances that are more heat-sensitive than others.

The two antioxidant plant substances lutein and zeaxanthin, for example (in pistachios and hazelnuts), cannot be influenced by the roasting process alone (2).

However, research has shown that total antioxidant activity in nuts generally decreases continuously during roasting (first half hour at 150 degrees Celsius) but actually increases again after a period of roasting (but never again at the high starting point of raw nuts). reached).

However, the latter was only the case after 60 minutes, which nobody in the household will practice. The antioxidant potential in the second half-hour of roasting increases because chemical reactions occur during the roasting process that creates new substances with antioxidant properties.

Does roasting lead to mineral losses?

Due to the loss of water during roasting and the minerals’ insensitivity to heat, the mineral content automatically increases slightly during roasting (1). With almonds, for example, the potassium value increases from 705 mg to 746 mg per 100 g, the magnesium value from 268 mg to 286 mg, and the iron value from 3.7 mg to 4.5 mg.

Does roasting almonds lead to vitamin losses?

The extent of vitamin loss through the roasting of nuts depends very much on the type of nut, the roasting temperature, and the roasting time so no uniform statements can be made here.

For example, the roasting of almonds and walnuts results in higher losses than the roasting of hazelnuts. With pistachios, on the other hand, there is almost no loss of vitamins.

The levels of alpha-tocopherol (the most active form of vitamin E) drop by 20 percent in almonds and 16 percent in hazelnuts after 25 minutes of roasting at 140 degrees Celsius. If the roasting temperature rises to 170 degrees Celsius, the vitamin E levels drop by 54 percent (almonds) and 20 percent (hazelnuts) after just 15 minutes.

The levels of riboflavin (vitamin B2) are not changed during roasting.

According to a study from 2010 (University of Hohenheim), the usual industrial peeling processes (which also include roasting) reduce the number of numerous ingredients in cashew nuts, e.g. B. beta-carotene, lutein, zeaxanthin, alpha-tocopherol, thiamine (vitamin B1), oleic acid (monounsaturated fatty acid) and linoleic acid (polyunsaturated fatty acid/omega-6 fatty acid).

Cashew nuts that are cracked and peeled using the Flores hand cracking method have the same vital substance values ​​as raw and untreated nuts. Flores hand cracking is a traditional method from the Indonesian island of Flores, in which the kernels are peeled cold, i.e. without roasting processes or other heating.

Does roasting nuts produce acrylamide?

The typical flavor and color of roasted nuts are the result of a specific chemical reaction that occurs during roasting: the Maillard reaction.

It is a reaction between the amino acid asparagine and the natural sugars found in nuts. If these two react with each other during dry heating to over 120 degrees, the brown color that is typical of roasting develops. However, it is precisely the Maillard reaction that can also produce harmful substances such as acrylamide, which is considered to be carcinogenic.

Since almonds have particularly high levels of asparagine, they are more susceptible to acrylamide formation than other nuts. In almonds, the formation of acrylamide begins at temperatures above 130 degrees and is significantly accelerated at temperatures above 146 degrees.

In the food industry, almonds are roasted at 140 degrees (23 minutes) to 180 degrees (11 minutes), which can lead to high levels of acrylamide formation.

The temperature usually promotes the formation of acrylamide more than the roasting time. Increasing the temperature from 139 to 151 degrees leads to a 33-fold increase in acrylamide formation (with a roasting time of 25 minutes) while increasing the roasting time from 20 to 25 minutes only increases acrylamide formation by a factor of 1.7 (at 160 Centigrade).

It is therefore better to roast almonds at lower temperatures and for a little longer, e.g. B. 25 minutes at 130 degrees.

Other nuts do not form as much acrylamide when roasted. Some amounts form in pistachios above 140 degrees Celsius (25 minutes), but not nearly as much as in almonds. In macadamias, walnuts and hazelnuts apparently no acrylamide is formed during roasting.

It is also interesting that European almonds have a significantly lower asparagine content and therefore produce significantly less acrylamide during roasting than US almonds.

Are raw nuts contaminated with bacteria?

Possible contamination with harmful bacteria is mentioned as a disadvantage of raw nuts, e.g. B. with salmonella, listeria, or E. coli, which could spread from the ground to fallen nuts. Contaminated water can also contaminate nuts.

However, studies show that only a few nuts are contaminated with bacteria. In samples, Salmonella was found in only 1 percent of the nuts, with macadamias showing the highest Salmonella levels in the rare cases of contamination, and hazelnuts the lowest. Pecans were not affected at all.

However, the contaminated nuts also had such low salmonella levels that they generally cannot lead to infection in healthy people. Nonetheless, in the US, all almonds must be pasteurized to kill any potential salmonella.

Roasting nuts eliminate harmful bacteria, making the nuts safer to eat in that regard.

Are nuts contaminated with mold toxins?

Mold can also reside on nuts without being seen or tasted. However, their toxic fungal toxins (aflatoxins) are carcinogenic and should therefore be avoided. If a nut is contaminated with aflatoxins, roasting is of no use either, since aflatoxins are extremely heat-resistant.

Food controls show that nuts from the tropics or subtropics are particularly contaminated, i.e. imported nuts, which ideally do not even end up on the market. Overall, it is said that the limit values ​​for nuts are rarely exceeded.

In any case, ground nuts are more likely to be affected by mold than whole nuts. Products that contain ground nuts, e.g. Nut biscuits, for example, are critical in this regard, so you should always grind nuts yourself just before eating.

If you harvest nuts yourself, you should definitely ensure that the nuts dry quickly and thoroughly and avoid moisture during storage.

Are roasted nuts still prebiotic?

Nuts and especially almonds or their brown skin are considered prebiotics, which means that they serve as food for the intestinal flora and can thus contribute to a healthy intestinal flora.

If almonds are now roasted, the question arises as to whether their prebiotic effect is retained. The results here are not entirely consistent. In a study from 2014, this question could initially be answered with yes. 48 subjects received 56 g of roasted (but unsalted) almonds daily for 6 weeks, which led to an improvement in their intestinal flora composition. The number of bifidobacteria and lactobacteria increased, while the harmful bacterium Clostridium perfringens was significantly suppressed.

However, a 2016 study on rats found that roasting reduced the prebiotic properties of almonds somewhat. Both raw and roasted almonds increased the number of bifidobacteria and lactobacteria and inhibited the proliferation of enterococcus bacteria. However, raw almonds were able to promote the population of bifidobacteria more than roasted almonds.

At the same time, the amount of ß-galactosidase, an enzyme that is produced by bifidobacteria and lactobacteria and is known for its intestinal health effect, increased more after eating the raw almonds. The enzymes that are harmful to the intestines, on the other hand, also decreased more clearly in terms of quantity, such as β-glucuronidase, nitroreductase, or azoreductase, which z. B. be formed by clostridia.

Are raw or roasted nuts easier to digest?

A digestion simulation in the laboratory in 2009 showed that roasted almonds are digested faster because they absorb less gastric juice and do not swell as much.

Roasted almonds, therefore, fill you up faster, but the saturation does not last as long as with raw almonds. The latter swell up more, fill you up better, but therefore also require a slightly longer digestion time.

How do you store raw nuts, like roasted nuts?

In any case, nuts should be stored properly and not eaten beyond their shelf life. Raw nuts (pistachios, pecans, walnuts, almonds) last about 1 year in the refrigerator (at 4 degrees Celsius or below) — shelled or shelled, according to a study from the University of California Agriculture and Natural Resources Department.

Roasted nuts should be consumed within a few days to a few weeks. It is best to put them in the fridge or (in winter) in a cool pantry until you need them.

Are Raw Nuts Healthier Than Roasted Nuts?

A 2017 study showed that roasting hazelnuts did not negatively impact their heart-protecting properties. For this study, 72 participants ate 30 g of hazelnuts daily for 4 weeks – either raw or roasted. Both forms of hazelnut significantly improved the cholesterol and apolipoprotein values ​​as well as the blood pressure of the test subjects.

A 2017 study found that roasting does not have a negative effect on pistachios’ protective effects against colon cancer. The influence of raw and differently roasted pistachios on cancer cells was examined. It was roasted at 141 to 185 degrees Celsius for 15 – 25 minutes.

Summary: Should nuts be eaten raw or roasted?

In summary, the above findings are as follows:

• Better eat raw nuts.
• Raw and roasted nuts contain almost equal amounts of calories, protein, fat, carbohydrates, and fiber. The differences are minimal.
• Buy raw nuts in season (autumn/winter – i.e. as fresh as possible) and store them in the refrigerator (no longer than 1 year).
• Give preference to local/European almonds and nuts.
• If you need roasted nuts, roast them yourself shortly before consumption or further processing in the oven, where you can set the temperature precisely.
• Ideally, roast at 130, but at most 140 degrees Celsius for about 15 to 25 minutes – as this minimizes the loss of vitamins, the fatty acids are hardly damaged and the likelihood of acrylamide formation is reduced.
• Only store roasted nuts for a few days. Their durability is low.
• When buying roasted nuts, look for good quality, and remember that roasted nuts often come with oil, salt, or sugar, which you may not want. Therefore, look carefully at the package or the list of ingredients.
• In general, roasting preserves the health benefits of nuts (anti-cancer, cardiovascular protection).
• However, harmful substances can form during roasting (acrylamide, trans fats), which can be avoided if you prefer raw nuts.
• If you need ground nuts, grind them yourself and always just before you eat them, so don’t buy ground nuts!
• Raw nuts can be contaminated with bacteria. However, the risk is small.
• Raw and roasted nuts can be contaminated with mold toxins if they have not been properly dried. Food controls show that the contamination usually remains below the limit values ​​and that imported nuts from the tropics/subtropics are more affected. Carry out measures to remove mold toxins from time to time.