How do different ingredients affect the fermentation time and structure of plant-based yoghurt-like products?

Abstract

The market of plant based dairy alternatives such as yoghurt alternatives continues to grow as more information on the environmental impact of traditional dairy products become available. The plant-based yoghurt alternatives come with a new set of problems, including longer fermentation times and poor gel structure formation. The aim of the project was to see if fermented yoghurt alternatives could be created based on pea, oat and chickpea protein powders at different weight percentages using two different bacterial strain mixtures of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The addition of potato starch was also studied due to the poor gel structure formation in some recipes. The project included an investigation into the fermentation time, texture, microstructure, spontaneous syneresis and viability of the created yoghurt alternatives. Results showed satisfactory fermentation times regarding food safety for all protein sources and both bacterial strain mixtures, but not all fermentations reached a final pH of 4.6 within the desired timespan (600 min). The texture analysis results showed that an increased protein powder concentration resulted in an increase in the texture properties of firmness, consistency and cohesiveness. Only the recipes with chickpea powder resulted in proper gel structures for all tested protein concentrations, although syneresis occurred at 2.5 wt% protein content after 1 day of cold storage. For pea and oat, protein percentages of 5 wt% or below resulted in phase separation. The addition of potato starch to the recipes resulted in reduced spontaneous syneresis and reduced phase separation for all samples. The differences in texture properties and phase separations were to some extent explained by the microstructures. For pea yoghurt alternatives, the network was made from mainly protein interactions from both denatured and partially denatured proteins. For chickpea yoghurt alternatives, it was made from a mixture of protein and starch networks. Oat yoghurt alternatives on the other hand, had mostly undenatured proteins, with some starch but no clear network. Conclusively, fermented plant-based yoghurt alternatives with varying properties were able to be created. However, further investigation on the suitability on a pilot-scale as well as investigation of problems that occurred during the study is needed. These included the curdling phenomenon of the chickpea concentrate and pH differences within separated samples.

Popular Abstract

The impact of using chickpea, oat and pea proteins to create plant-based yoghurt alternatives.

The interest in plant-based dairy products such as yoghurt, ice cream and cheese alternatives have increased by 53% in the US, between 2018-2020 and is thought to increase further. Plant-based yoghurt alternatives can be produced from a variety of different plant-sources used as a replacer for dairy and the properties of the final products will vary dependent on the source. But how do different ingredients affect the creation of yoghurt alternatives and the final product?

The process of creating plant-based yoghurt alternatives is similar to the process used to make dairy yoghurt. The process is fermentation, which is when bacteria are added to the product and their activity will affect several properties, including the taste and pH. As a result of the pH change the typical yoghurt structure is created. However, some plant-based yoghurt alternatives require additional stabilizers, since the structure is too weak or will result in water separating from the yoghurt, which is regarded as a quality issue. It has also been observed that plant-based alternatives have longer fermentation times which has been seen as a problem for food safety and production.

Chickpea, oat, and pea protein powders were used at 10, 5 and 2.5% protein content to investigate if plant-based yoghurt alternatives could be created and fermented within a reasonable time. The effect of two different commercial starter cultures and additional potato starch, as a stabilizer, was also looked at. The fermentation times were within limit when considering one of the main food safety issues commonly seen in plant-based yoghurt alternatives. It was also seen that fermentation took the longest for the yoghurt alternative made on pea than it took for the other two sources. Furthermore, higher protein content resulted in stronger textures. All chickpea recipes, no matter protein content, created structures without water separating during fermentation. However, this was not the case for oat and pea, which had heavy separation at 5% and 2.5% protein content, unless potato starch was added.

These findings contribute to the knowledge on the creation of pea, oat and chickpea yoghurt alternatives based on protein powders, especially at lower percentages of protein content, where knowledge previously has been limited. Furthermore, previous studies on chickpea as a base of yoghurt alternatives have not been found and this study is therefore a first step on how the source may be a good future candidate for plant-based products, since it created superior structures compared to the other two sources in the study. There was an interesting curdling effect that was seen for some chickpea recipes which would need further investigation. Conclusively, using these plant sources for yoghurt alternatives seem promising, however more research needs to be done.

• author: Holmgran, Nicki and Svendsen, Jens
• supervisor: Åsa Håkansson; Randi Phinney; Jeanette Lindau
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM05 20211
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Food Engineering, Livsmedelsteknik, plant-based, yoghurt, oat, pea, chickpea
• language: English
• id: 9047670
• date added to LUP: 2021-06-09 11:07:15
• date last changed: 2021-06-09 11:07:15