What happens when processing soy protein?

Published 11. February 2020

The effect of processing on nutrient structure, composition, and digestibility of soy protein

Soybean meal (SBM) is one of the most important sources of protein used in animal diets all around the world. The Agilia™ team have unlocked previously hidden nutritional and functional properties of SBM thanks to a unique manufacturing process which delivers a consistent, high-quality, protein-rich product with every batch produced.

Mai Anh Ton Nu Ph.D.,
Animal Nutritionist and R&D Manager, Agilia

EFFECT OF ALPHASOY™ PROCESSING ON
PROTEIN AND AMINO ACID QUALITY

Mechanical and chemical factors affecting protein quality

The protein content of diets and its quality are key to ensuring high levels of performance. Protein quality is determined not just by analysis of the raw material but also by the utilisation capacity of the individual animal. Neither the animal nor the raw material remains consistent, so the quality and quantity of protein in the diet vary widely.

Protein quality can be influenced by several factors including the choice of raw material, use of additives such as enzymes, probiotics, acidifiers and yeast derivatives, the health status of the animal, and the processing techniques used on the raw material or finished feed.

Knowledge about the effects of processing raw materials and feed has increased substantially following decades of research. Processing can reduce and inactivate anti-nutritional factors as well as decrease microbiota levels including pathogens. Processing can also change feed ingredients or diets physically through agglomeration or hydrolysation, leading to structural changes.

One benefit of processing is that it can improve the digestibility of certain nutrients including starch and protein. However, specific processing techniques or conditions may also deteriorate the digestibility of protein, which will negatively affect animal performance. Deteriorated protein quality does not only result in lower protein and amino acid digestibility, with an associated adverse effect on gut health conditions, but it also has an impact on the environment through increased nitrogen excretions.

Protein can be over-processed in several ways due to unfavourable processing conditions which are influenced by time, temperature, moisture and water activity, pressure, particle size and pH (Hulshof, 2016). All these processing factors need to be monitored closely to ensure high protein quality in final products.

During processing, there will be physical or chemical changes to the protein in feed ingredients or diets. However, when overprocessing does occur, this might result in severe structural and characteristic changes to the protein that negatively influence its quality. Physical changes to a protein can include the shift from its primary structure to the secondary or even tertiary structure. Having been denatured by the processing conditions, the protein may refold in a different configuration, affecting its digestibility. Chemical changes to proteins include the formation of iso-peptides, protein-oxidised lipid interactions, proteinpolyphenol interactions, cross-link reactions and the Maillard reaction (Salazar-Villanea et al., 2017). The Maillard reaction causes a reduction in the availability of amino acids and proteins.

Protein quality parameters

A significant concern in SBM processing is whether processing will damage the availability of amino acids, especially lysine. Agilia™ uses the expertise and experience of its production team to control the manufacturing process of AlphaSoy™ products, making sure that the processes used, improve the crude protein and amino acid availability of the ingredient.

Heating of SBM is necessary to inactivate trypsin inhibitors, but overheating will reduce the digestibility and concentrations of lysine and other amino acids (González-Vega et al., 2011; Stein, 2012). In particular, lysine is highly susceptible to damage by heat treatment. There are two main parameters to detect heat damage of protein in the final product.

Available or reactive lysine
The ε-amino group present in lysine is especially reactive if reducing sugars are present. The reaction of lysine with sugar during the Maillard reaction at the first stages creates a complex compound that renders lysine unavailable to animals, even though the analysed value of lysine will not change. The amount of lysine that still possesses its reactive ε-amino group after processing represents the amount of undamaged lysine that remains available to the animal, known as reactive or available lysine.

The lysine: crude protein ratio
The ratio between lysine and crude protein (Lys: CP) is a simple but highly accurate measure of heat damage. When an ingredient is heat-damaged to an extreme level (final stage of Maillard reaction), the concentration of lysine is reduced, but the concentration of crude protein is not (González-Vega et al., 2011). For SBM, a Lys: CP ratio of 6 and above is generally accepted as an indicator of good protein quality.

The AlphaSoy™ manufacturing process does not impact the percentage of available lysine in total lysine as well as the ratio of lysine to crude protein (Figure 1), demonstrating that no damage or loss of lysine is caused by the applied processing. In addition, the measured increase in digestibility of available lysine indicates an increased net benefit of the AlphaSoy™ process to the animal.

Processing AlphaSoy

Improvements in protein and amino acid digestibility

The most accurate way to evaluate the protein quality of a feed ingredient or diet is through in vivo digestibility experiments. The effect of the AlphaSoy™ manufacturing process on enhancing the digestibility of protein and amino acids in SBM has been tested in both weaned pigs and broilers.

Weaned pigs
The unique AlphaSoy™ manufacturing process significantly increases the digestibility of crude protein and all key amino acids by 3% (P < 0.05, Figure 2) in piglets, as proven in a digestibility study conducted at the University of Alberta, Canada in 2017 (Ton Nu et al., 2018).

The study evaluated the digestibility of protein and amino acids in SBM before and after processing (AlphaSoy™) using ileal-cannulated weaned pigs of 10 kg bodyweight.

Poultry
Kim et al. (2018) investigated the effect of the unique AlphaSoy™ manufacturing process on the digestibility of crude protein and amino acids in SBM before and after processing in broilers.

 

The manufacturing process of AlphaSoy™ products improved the digestibility of crude protein and amino acids relative to SBM. (See Figure 3).

On average, the SID of crude protein was 2% higher in AlphaSoy™ (after processing) compared to SBM (before processing). In addition, the actual ileal digestibility of most indispensable and dispensable amino acids was higher in AlphaSoy™ compared to SBM.

The mechanism behind the processing effects that improve
protein and amino acid digestibility for all species

It is likely that the protein structure of SBM is changed during processing, allowing better access for endogenous digestive enzymes, regardless of which species it is fed to.

In addition, the the AlphaSoy product's manufacturing process reduces anti-nutritional factors to safe levels, resulting in a decrease in stress on the digestive tract and leading to reduced losses of endogenous nitrogen, which is particularly important for young and developing animals. The improved nutritional value of AlphaSoy™ relative to SBM allows the plant- and animal-based protein sources in the diet to be substituted for AlphaSoy™.

The increased bioavailability of nutrients and improved quality of AlphaSoy™ products are specifically designed to support gut health and development of young swine and poultry animals, making it a first-choice product to be used in antimicrobial reduction feeding strategies.

EFFECT OF ALPHASOY™ PROCESSING ON
CARBOHYDRATES AND ENERGY VALUE

Positive changes to the carbohydrate profile of SBM

Traditionally, SBM is regarded as a protein source. As such, the energy value of SBM, which is almost as high as corn/maize, is forgotten. This traditional view means that only half of the potential value of SBM is unlocked. In the case of AlphaSoy™, all nutrients are considered in the ingredient matrix, and the full potential of the raw ingredient is maximised. There are three sources of energy in any feed ingredient and diet; protein, fat, and carbohydrates. Of these three, carbohydrates are the most important and dominant energy source. There are two types of carbohydrates: digestible and fermentable carbohydrates.

Digestible carbohydrates
Digestible carbohydrates are very easy to digest and are ideal for immature digestive systems like those in young animals or weaned piglets. Starch, monosaccharides (e.g., glucose) and disaccharides (e.g., sucrose and lactose) are all considered to be digestible carbohydrates (Boisen, 2005).

Fermentable carbohydrates
In contrast, fermentable carbohydrates have a very complex structure and cannot be digested by digestive enzymes. To use the energy from these carbohydrates, the animal needs help from the microorganisms in the gut through a process of fermentation. This is a less efficient way of harvesting energy compared to using digestible carbohydrates. As a result, digestible carbohydrates have almost double the energy value of fermentable carbohydrates (11.7 vs. 7 kJ/g, respectively, Boisen, (2005)).

The AlphaSoy™ manufacturing process is designed to dramatically change the fibrous structure of SBM by boosting the digestible carbohydrate content and reducing the fermentable carbohydrate content of SBM. As a result of the unique processing techniques used, AlphaSoy™ has the highest carbohydraterelated energy value of all comparable products (Figure 4). For example, the energy value contributed by digestible carbohydrate in AlphaSoy™ is almost nine times higher than in soy protein concentrate (SPC). The total energy value provided from the carbohydrate fraction is nearly double the value of SPC (Figure 4).

Increased net energy values after processing

The unique carbohydrate profile of AlphaSoy™ products contributes to a unique net energy value when compared with other unprocessed soy protein products. The energy value of AlphaSoy™ products is up to 16% higher than comparable products based on the published Danish Feeding Table (SEGES, 2017; Figure 5).

This uplift in energy is seen regardless of animal species. A joint study in weaned piglets conducted by leading research sites in the USA and Denmark also showed that AlphaSoy™ products had the highest digestible and metabolisable energy of all soy protein products. The energy level in AlphaSoy™ products was a significant improvement on the energy level in conventional SBM, owing to the specific production process (Figure 6). The same trends in energy uplift were proved in both data pools.

The effect of the the AlphaSoy product's manufacturing process on energy is universal, crossing different species as shown by Kim et al. (2018) who also picked up a 15% higher apparent metabolisable energy (AME) in broilers (Figure 7).

PROCESSING IS KEY TO UNLOCKING VALUE

SBM can vary hugely in its consistency and quality. In young animal diets, feeding an un-processed SBM can lead to reduced performance. Therefore, the the AlphaSoy product's manufacturing process is vital in creating a consistent, high-quality, protein-rich ingredient. Processing improves the ingredient structurally, compositionally and nutritionally by:

  • Improving the nutritional matrix value of SBM – tailoring it to the needs of the animal
  • Unlocking 2 - 3% more digestible protein and amino acids in piglets and broilers
  • Boosting the net energy value by up to 16% in piglets and broilers

As a result of this unique profile, AlphaSoy™ delivers better feed performance in terms of body weight gain, feed intake and feed conversion rate than all competing soy protein products. It also delivers the same performance as animal proteins, but at a much lower cost. Their nutritional value combined with their functional properties makes AlphaSoy™ products your first choice when designing antimicrobial reduction feeding strategies.

References

Boisen, S. (2005). A New Concept for Practical Feed Evaluation Systems, Research Centre Foulum.

González-Vega, J.C., Kim, B.G., Htoo, J.K., Lemme, A., and Stein, H.H. (2011). Amino acid digestibility in heated soybean meal fed to growing pigs. J. Anim. Sci. 89, 3617–3625. doi:10.2527/jas.2010-3465.

Hulshof, T., Bikker, P., van der Poel, A.F.B. and Hendriks, W.H. (2016). Assessment of protein quality of soybean meal and 00-rapeseed meal toasted in the presence of lignosulfonate by amino acid digestibility in growing pigs and Maillard reaction products. Journal of Animal Science. 94(3). DOI: 10.2527/jas.2015-9700.

Kim, E., Rho, Y., Masey O’Neill, H., Schulze, H., and Kiarie, E. (2018). Standardized ileal digestibility of amino acids and apparent metabolizable energy in processed soybean meal (AlphaSoy™) fed to broiler chicks. Poster presented at Poultry Science Association 2018 Annual Meeting; 2018 July 23 – 26, San Antonio, Texas.

Navarro, D. (2014). Amino acid digestibility and concentration of energy in processed soybean and rapeseed products fed to pigs. Master Thesis, the University of Illinois at Urbana-Champaign.

Salazar-Villanea, S., Bruininx, E.M.A.M., Gruppen, H., Carré, P., Quinsac, A., and van der Poel, A.F.B. (2017). Effects of toasting time on digestive hydrolysis of soluble and insoluble 00-rapeseed meal proteins. Journal of the American Oil Chemists’ Society. 94(4). 619-630.

SEGES. (2017). FODERVÆRKTØJER [WWW Document]. SEGES Pig Prod. [On-line]. Available from: https://svineproduktion.dk/Viden/Paa-kontoret/Oekonomi_ledelse/Beregningsvaerktoejer/Fodervaerktoejer. Accessed 12.10.18.

Stein, H.H. (2012). Soybean meal fed to pigs, in The Nutritive Value of U.S. Soybean Meal. Atlanta, GA.

Ton Nu, M. A., Schulze, H., and Zijlstra, R.T. (2018). Processing of soybean meal enhanced the ileal digestibility of protein and amino acids in weanling pigs. Poster presented at 14th International Symposium on Digestive Physiology of Pigs; 2018 August 21 – 24, Brisbane, Australia.