Walnuts, hazelnuts, cashews and almonds are just a few of the little powerhouses that have a positive effect on our health. They not only contain important minerals such as phosphorus, magnesium and calcium. Dietary fiber, unsaturated fatty acids and essential vitamins also provide these in sufficient quantities. However, many do not know that the unroasted variants in particular have a healthy effect on our body.
Heat makes fatty acids dangerous
Due to the high heat during the roasting process, the unsaturated fatty acids contained are converted into saturated ones. In doing so, they lose their positive cholesterol-lowering effect. In addition, harmful free radicals can arise, which can cause cell damage and thus cancer. This can be prevented by roasting in the low or medium temperature range. Then heat-resistant vitamins are more likely to be retained, which gives the gently roasted nut a very good rating overall. For consumers, however, it is not always clear at first glance the heat with which products available in the supermarket were processed. That makes the right choice difficult.
Not all nuts are equally affected
While walnuts are particularly sensitive to heat because they contain a large number of polyunsaturated fatty acids, other types of nuts are different. In the case of almonds and hazelnuts, for example, a particularly high decrease in vitamin E was found due to heat. Due to their amino acid profile, almonds also form acrylamide, which is considered to be carcinogenic. But antioxidants that are not heat-resistant are also likely to be lost during the roasting process. But there are also a number of antioxidant substances that survive at 150 degrees Celsius for more than 30 minutes and then even increase again due to newly created chemical reactions. However, the original number of antioxidants found in raw nuts is no longer achieved.
Prebiotic effect not clear
Probiotic foods have been on the market for a number of years. Bacteria contained in it should support the stomach and intestines in digestion. The same applies to indigestible plant components, also called prebiotic ingredients, which support the microorganisms living in the intestine and contribute to a favorable intestinal environment in the long term. These are mostly dietary fibers such as inulin or oligofructose, which are also found in nuts. However, it is not clear how the roasting process affects the prebiotic ingredients. In a study from 2014, an improvement in the intestinal flora was observed in 48 test subjects for 6 weeks through the consumption of roasted almonds. However, a study from 2016 showed in the experiment with rats that unroasted almonds had a stronger positive effect on the intestines of the animals compared to the roasted variant. That leaves open which version of the almond is ultimately more health-promoting for humans.
If in doubt, roast yourself
But if you don’t want to put up with raw nuts in terms of taste, you can simply roast the nuts and seeds yourself in the oven. For this purpose, the consumer center in South Tyrol recommends a maximum temperature of 130 to 140 degrees Celsius and a rather short roasting time of 15 to a maximum of 25 minutes. The roasting also kills any germs that may not survive the roasting process. However, mold toxins are problematic as they survive in the nuts despite the heat and can lead to secondary diseases. The main disadvantage of raw nuts is that they perish quickly. The unsaturated fatty acids it contains mean that if stored incorrectly, they will go rancid within just a few weeks. It is therefore recommended to keep them in the refrigerator at 4 degrees Celsius or lower. Then they even last up to a year.