Why is it important to consider safety?
The use of plant proteins in analogue products is driving the development of novel approaches to create products with characteristics associated with meat, dairy or egg products. Examples of these processes include fermentation, extrusion, shearing, tissue disruption and homogenisation. However, aspects surrounding the microflora of newly considered plant proteins are relatively unknown, in terms of composition and their interactions during a product’s life and during processing. Application of the aforementioned manufacturing processes may therefore pose certain challenges. This highlights the importance of considering safety when developing these products.
For example, it is worth considering the creation of unknown microbial community dynamics due to cross-feeding during the fermentation of products containing plant proteins. This cross-feeding will introduce microflora from plant proteins, along with any secondary metabolites that result.
Plant-based alternative products are also likely to require different ingredients than their animal‑based counterparts to achieve the desired texture, colour and flavour. These differences could impact microbial survival and growth in the finished product.
What safety factors are there to consider?
Plant proteins differ in structure from their animal‑based alternatives, resulting in variation in heat transfer and cooling characteristics. The validation of processes is important to verify the reduction of microbial load to an acceptable level, or to limit/reduce growth of spoilage and pathogenic microorganisms.
Plant-based products often struggle to recreate the diverse functionalities of egg and dairy products
Other issues include potential variability in the organisms present between batches, which could be influenced by climate, location of origin, time of harvest and processing steps in ingredient preparations. The variation in microbial load and the nutrient composition of plant proteins present challenges. Risk assessments, therefore, should consider the pathogens that could be present and the potential for these to grow in the final product. Robust specification of the plant protein ingredients is crucial to mitigate safety risk and should be included in the assessments.
As plants grow, their leaves and surfaces could be exposed to pathogens through contact with wildlife, insects and soil. One of the main risks of contamination will be from spore formers, which are known to be found both in soil and the wider environment. Spore formers are more resilient to heat treatments and some species such as B. cereus can produce toxins if they survive and grow in the final product or intermediates. Other species of Bacillus genus cause the spoilage of products leading to changes in product appearance or potential formation of off odours in the final product.
Case study: plant protein batch diversity – Upfield Research & Development BV
In a bid to establish batch-to-batch variability, we undertook advanced microbial profiling studies using sequence-based identification of different batches of a plant-based ingredient (50-60 percent protein). Microbial profiling is a culture-independent technique used to identify the microbial population in an ingredient. This approach enables the identification of organisms in a sample, reducing the bias of cultivating fastidious microorganisms.
We isolated and identified microorganisms present in a concentrated faba bean solution that have the potential to grow in the following conditions:
- The faba bean solution post pasteurisation during storage at 60°C in holding tanks
- The final product during the course of its shelf life.
This microbiological analysis was carried out before and after pasteurisation to isolate viable organisms which were identified by matrix‑assisted laser desorption/ionisation-time of flight (MALDI‑TOF) analysis.
What was the result?
Microbial profiling, of more than five batches, found that the predominant flora present in the faba bean ingredient pre-pasteurisation were organisms from the Bacillaceae family.
Faba beans have received significant attention recently as an important ingredient in alternative protein products
Analysis of the faba bean solution pre‑pasteurisation showed that Bacillus spores (B. subtilis and B. licheniformis) were present prior to treatment at low levels. The results from the post-pasteurisation solution revealed that the spores of B. subtilis and B. licheniformis were detected and thus were able to germinate during holding of the pasteurised product. In addition to Bacillus spp, the thermophilic spore former Geobacillus stearothermophilus was also detected in the plant proteins and was able to grow and sporulate in the faba bean solution stored at 60°C.
How was this useful to Upfield?
By studying the presence of microorganisms in faba bean protein and establishing potential safety and quality issues, we have helped Upfield to:
- confirm the need for robustness of faba bean ingredient specifications
- develop mitigation plans for processes by making adjustments in processing and storage conditions.
As a result, this study supported Upfield to ensure product safety and limit possible spoilage issues over product shelf life when using this plant-based protein ingredient. The study provided a better understanding of the microflora of this ingredient and enabled the verification of suitable storage temperature, to minimise growth during storage in the holding tank. It also enabled Upfield to set specifications for its plant-based ingredients, ie, to customise/adapt process details to minimise growth during production until the product is packed.
Why is it important to consider the functionality aspect?
Numerous animal-derived products such as egg and milk have been used in industry for many years, thus establishing favoured recipes and processes. These ingredients serve a purpose (or a function) in the final product. For example, eggs set when heated and they are also effective for emulsification and foaming. This makes them useful for baked products. Milk can be foamed, whipped or coagulated by acid, making it an extremely versatile ingredient used in a broad range of products, including drinks, creams, yoghurts and various types of cheeses.
VODCAST Episode Eighteen (special on plant-based #2): Female leaders discuss alternative proteins
To remove a functional ingredient requires replacement of the ‘function’ with an alternative ingredient, otherwise the result will be different in structure, texture and performance.
How does ingredient functionality potentially impact on the final product and consumer liking?
Functionality plays an important role in determining the texture, structure and microstructure of the product; if any of these change then the product perception changes. An example is removing egg from a mayonnaise. Egg helps to emulsify the oil and water-based ingredients. If you do not replace the emulsification function, then the product will not remain a stable emulsion. If dairy proteins are removed from cheese, not only will texture function need to be replaced but cheese melting and stretching properties will need to be addressed too.
What type of functionality issues are there specifically for plant-based ingredients?
Both egg and dairy proteins have multiple functionalities. These ingredients deliver gelling, foaming and emulsifying properties, among many others, in a single source. Functionality is largely driven by ingredient solubility. As plant proteins have very low solubility compared to egg and dairy their function is overall low. Though different plant proteins have different functionalities, there is no single plant protein that delivers the range of functionalities that egg or milk does. This means that every product category requiring egg or dairy protein replacement will need a thorough assessment of various plant‑based ingredients, to match the desired function that needs replacing. And this is not a simple process. Replacing the gelling properties of egg, for example, can be difficult. The gelling property requires specific proteins that not only denature at higher temperatures but then coagulate and stick together. This is an intrinsic property of the protein that can’t be changed easily. The same principles apply to dairy protein.
What can food businesses do to avoid these issues in their plant-based products?
Understanding the functionality of all their ingredients and how they interact with each other is key. Discerning the functionality of any ingredient they identify as a potential replacement is also vital. Together, these will help them make necessary adjustments to the recipe or process.
What other issues must be addressed when introducing plant-based ingredients to a formulation?
Egg and dairy ingredients used in product applications deliver white colour and neutral or dairy-like flavours that are appealing to the consumer. Plant proteins typically have cereal, pulses or oil seed (off-) flavours that become strongly pronounced in dairy-like food formulations and colour delivery ranging from off-white to dark brown and even grey. Both off-flavour and off-colour components are intrinsic to plants and need to be addressed when used in final product applications.
Acknowledgement
The authors would like to thank Sarma Nelissen-Manurung for her contribution to the article and assistance during the study.
Reference
- . https://www.prnewswire.com/news-releases/global-plant-based-food-market-is-expected-to-reach-74-2-billion-by-2027–301380153.html#:~:text=The%20plant%2Dbased%20food%20market,in%20the%20plant%2Dbased%20market.
