In a pig study, salami, bologna and beef jerky reached a DIAAS of 120 to 128 (adults), about as much as raw ground beef. Curing, fermenting and drying did not harm the protein. Of all things, well-done ground beef scored worst. The DIAAS says nothing about salt, fat or health, though.
The study
Bailey et al. 2020 fed eight meat products to pigs and determined the DIAAS for each. The processed products were commercially made:
- Salami: cured, fermented and fully cooked, made from pork
- Bologna: a cured, cooked sausage made from pork and beef, similar to German Fleischwurst or Lyoner
- Beef jerky: cured, dried beef
- for comparison: raw and cooked ground beef, plus beef roast at three levels of doneness
Ham was not included. The studies provide no measured values for it.
The results
Line = 100, from here on fully usable. DIAAS for adults, measured in pigs. Data: Bailey et al. 2020, Table 6.
| Product | Protein g/100 g | DIAAS young children | DIAAS adults |
|---|---|---|---|
| Salami | 17.1 | 107 | 120 |
| Bologna | 11.9 | 118 | 128 |
| Beef jerky | 48.9 | 102 | 120 |
| Ground beef, raw | 18.1 | 111 | 121 |
| Ground beef, cooked | 30.6 | 92 | 99 |
Amino acid digestibility did not differ between salami, bologna and jerky. For most amino acids it was slightly below that of raw ground beef, but the DIAAS still stayed high. All three count as excellent protein sources for adults. The authors write that processing into salami, bologna and jerky did not reduce protein quality. Lysine, the scarcest amino acid in many plants, was plentiful in all the meat products.
Why processing does no harm
The authors name several possible reasons:
- Curing salt protects. Ingredients like nitrite and table salt slow down oxidation during processing. This may preserve the structure of the proteins until digestion.
- Even cooking in the casing. Salami and bologna are made from ground meat, but they are heated from the outside inside a casing. That probably cooks more evenly.
- Moderate temperatures. The sausages were cooked to a core temperature of about 71 °C.
Well-done ground beef was a different story. According to the authors, its lysine and histidine contents went down, and the DIAAS dropped to 99. They suspect heat damage from oxidation, helped along by the large surface area of the ground meat. More on this in the article Cooking, frying, roasting.
Sausage as a partner for bread
Because meat contains a lot of lysine, the authors say it can complement grains, which lack exactly this amino acid. Calculated with the proteinscore database:
| Meal | DIAAS | |
|---|---|---|
| 100 g whole-grain bread | 45 | open |
| 100 g whole-grain bread + 30 g salami | 93 | open |
| 60 g toast + 50 g bologna-style sausage | 113 | open |
What the DIAAS doesn't tell you
The DIAAS only rates the protein. Moughan & Lim 2024 stress that it says nothing about other health properties of a food. Salt, fat, nitrite or additives play no role in it. So a high DIAAS doesn't make a sausage a healthy food. It only means its protein is easy for the body to use.
Limitations of the study
- One US-made product of each type was studied, in six to eight pigs. Recipes in other countries may differ.
- The study did not measure lysine as "reactive" lysine. Experts recommend this for strongly heated foods, because heat damage can otherwise be missed (FAO sub-committee 2012).
- The study was funded by a US cattle producers' association.
Frequently asked questions
Does sausage have high-quality protein?
In the study by Bailey et al. 2020, yes: for adults, salami reached a DIAAS of 120, a cooked sausage (bologna) 128 and beef jerky 120. That is on the level of raw ground beef (121).
Is beef jerky a good protein snack?
In terms of protein, yes. The jerky tested contained almost 49 g of protein per 100 g and reached a DIAAS of 120. The DIAAS says nothing about salt, sugar and other ingredients.
Does that make processed meat healthy?
That cannot be derived from the DIAAS. It only rates the protein. Experts stress that it says nothing about other health properties of a food.
How does your meal score?
Go to the calculatorSources
- Bailey, H. M., Mathai, J. K., Berg, E. P. & Stein, H. H. (2020): Most meat products have digestible indispensable amino acid scores that are greater than 100, but processing may increase or reduce protein quality. British Journal of Nutrition 124, 14–22. doi:10.1017/S0007114520000641
- Moughan, P. J. & Lim, W. X. J. (2024): Digestible indispensable amino acid score (DIAAS): 10 years on. Frontiers in Nutrition 11, 1389719. doi:10.3389/fnut.2024.1389719
- Moughan, P. J., Gilani, S., Rutherfurd, S. M. & Tomé, D. (2012): Report of a Sub-Committee of the 2011 FAO Consultation on “Protein Quality Evaluation in Human Nutrition”, with appendix by Moughan & Rutherfurd: True ileal amino acid and protein digestibility for selected human foods. FAO, Rome.
Values for individual foods and where they come from are listed under Data & sources. How proteinscore calculates is explained under Method.