Can you eat tempeh raw?

In this article, we will answer the question “Can you eat tempeh raw?” and discuss what are the risks of eating raw tempeh. Tempeh is a traditional Asian food made from fermented soybeans.

Can you eat tempeh raw?

Yes, you can eat tempeh raw. Tempeh may be eaten cooked or raw. The most popular method to prepare tempeh in Indonesia is frying. The nutritional properties of food, including tempeh, changes, depending on the cooking method applied.

There are advantages and disadvantages of eating tempeh raw, which will be discussed in this article. 

What are the benefits of eating Tempeh raw?

Tempeh is a very nutritious food and a source of important amino acids and iron. When consumed raw, the amino acids are in their totality. Heat treatments can decrease the amount of amino acids in tempeh, as well as the amount of iron (3).

During the fermentation process, the enzymatic digestion of substrates, leads to an increased amount of free amino acids, water-soluble nitrogen compounds, free fatty acids, and to the development of characteristic flavor (2). 

Does cooking change the nutritional value of tempeh?

Yes, cooking changes the nutritional value of food, including tempeh. Studies show that the  frying process might break down isoflavone glycosides into isoflavone aglycones, which can increase their bioavailability. 

Raw tempeh contains the highest levels of daidzein and genistein, compared to tofu or soybean drinks. However, the process of tempeh deep frying significantly (up to 45%) reduces the total isoflavones content (2).

A study showed that frying tempeh in coconut oil significantly reduced the levels of free fatty acids by releasing them into the frying oil. Deep Fat frying also decreased the levels of amino acids after 5 min and moreover after 7 min, where lysine and cysteine were the most susceptible to heat destruction compared to other amino acids (3).

However, a study showed that tempeh, both raw and cooked, is a source of immune-stimulating compounds, probiotics live or dead. Probiotics are microorganisms that, when incorporated in the diet in adequate amounts, may offer health benefits to the host (7).

Studies showed that both uncooked and cooked tempeh have positive effects in the immune system, due to the presence of probiotics by uncooked tempeh and due to the presence of paraprobiotics, i.e. heat-killed probiotics that can stimulate immune response, by cooked tempeh (3). 

What are the risks of eating Tempeh raw?

Here are the reasons why most people think that tempeh should not be eaten raw.

Is eating tempeh raw safe?

Eating tempeh raw is not always safe. Naturally occurring bacteria are used in the fermentation process, which occurs at room temperature (or even warmer, more humid conditions). If done poorly, this procedure might offer a number of serious health hazards.

Before making any fermented food, it is necessary to sanitize the equipment. Everything from the beginning of the procedure until its final packaging is included in this category. Workers handling the food, mixing equipment, machinery, and surfaces, as well as the packaging itself, are just a few of the factors to consider.

Foodborne infections may result if contaminated equipment used in the food processing is not sterilized. Rare but deadly illness, rhinocerebral mucormycosis may be caused by the fungus Rhizopus, which is found in fermented tempeh foods.

R. microsporus has been mostly isolated from environmental and clinical samples such as soil, wood chips, saw mill dust, and human tissue, but it has also been isolated from tempeh in Indonesia. In addition, studies reported the gastroenteritis outbreak in North Carolina in 2012 caused by the consumption of unpasteurized tempeh (3).

Other sources of contaminants in tempeh are poor handling, unhygienic facilities and the use of river water for the production of tempeh, which is not uncommon in the traditional production in Indonesia. This could lead to the contamination by bacteria Klebsiella pneumoniae and Citrobacter freundii (3).

Therefore, it is not safe to eat tempeh raw. Pasteurizing is a heat treatment (165° F for 15 minutes) usually applied to tempeh, which is able to kill pathogens like Salmonella, Listeria, and E. coli O157:H7, as well as controlling cross contamination from contact with bare hands, surfaces, and raw materials.

Is tempeh safely produced?

Not always is tempeh safely produced following good producing practices or under hygienic conditions. A surprising quantity of tempeh is made in or even imported from household kitchens. 

Tempeh is produced mostly by a small scale home industry with poorly controlled fermentation procedures that in addition are carried out without sufficient hygienic precautions. 

Therefore, there are various types of microorganisms that can participate during the process of fermentation, and natural contamination is always possible. Moreover, there is no standard on making tempeh and its starter. This causes many variations in the manufacture of tempeh in many areas and leads to inconsistencies in quality and safety of tempeh (4).

What are the additional benefits of cooking tempeh?

An additional benefit of cooking tempeh is that cooking is able to reduce the levels of ethyl carbamate in food, when this compound is present.

Biogenic amines and ethyl carbamate are toxic substances which can be generated in foods, mainly by microbial enzymatic activity. Tempeh is a possible food source of this compound.

Ethyl carbamate (urethane) has mutagenic and carcinogenic properties, and can be formed from reaction with ethanol and naturally occurring carbamyl phosphate during the fermentation process. 

Both compounds mainly result from yeast metabolism; ethyl carbamate can also be formed by the reaction of ethanol and urea produced naturally from amino acids like arginine and citrulline (5).

According to studies, cooking may reduce the levels of ethyl carbamate in tempeh products.

Conclusion

In this article, we answered the question “Can you eat tempeh raw?” and we discussed what are the risks of eating raw tempeh.

Reference

1. Qin, Pingxu, Taoran Wang, and Yangchao Luo. A review on plant-based proteins from soybean: Health benefits and soy product development. J Agric Food Res, 2022, 7, 100265.
2. Jeleń, Henryk, et al. Determination of compounds responsible for tempeh aroma. Food Chem, 2013, 141, 459-465.
3. Ahnan‐Winarno, Amadeus Driando, et al. Tempeh: A semicentennial review on its health benefits, fermentation, safety, processing, sustainability, and affordability. Comprehen Rev Food Sci Food Safe, 2021, 20, 1717-1767.  
4. Anggriawan, Riyan. Microbiological and food safety aspects of tempeh production in Indonesia. The Economist, 2001.
5. Nout, M. J. R., et al. Effect of processing conditions on the formation of biogenic amines and ethyl carbamate in soybean tempe. J Food Safe, 1993, 13, 293-303.
6. MacDermott, Richard P. Treatment of irritable bowel syndrome in outpatients with inflammatory bowel disease using a food and beverage intolerance, food and beverage avoidance diet. Inflamm bowel dis, 2007, 13, 91-96.
7. Soka, Susan, et al. Impact of tempeh supplementation on mucosal immunoglobulin A in Sprague-Dawley rats. Food sci biotechnol, 2015, 24, 1481-1486.