Improving the digestibility of alternative proteins using high moisture extrusion for plant-based fish analogues

Abstract

The consumption of plant-based, food alternatives is increasing globally. Yet, the digestion of plant proteins is hindered by various antinutritional and external factors. Therefore, delving into the extent of plant protein digestibility in the human body becomes essential, alongside efforts to enhance this process. The main aim of this present work was to determine the digestibility of plant-based fish analogues based on a mixture of yellow pea (80%), and microalgae (1.85%) protein. Four samples were produced using the high moisture extrusion technique assigned to A, B, C, and D, with the extrusion temperature profiles decreasing sequentially for each sample by 5°C each zone. Protein digestibility of the obtained products was studied using an in-vitro digestion according to the guidelines of INFOGEST protocol. Real tuna underwent in-vitro digestion as a control for animal-derived protein source.

The protein content remaining after digestion was measured using the Bradford and Dumas method. The results obtained from both methods were compared and a similar trend was observed. The plant-based fish analogues and real tuna showed a decrease in protein content after the digestion by 76-77% and 84%, respectively, compared to the initial protein concentration. Statistical analysis proved that the temperature profile in high moisture extrusion has a significant effect on the protein content after digestion. Sample C had the second lowest temperature profile and highest digestion (zone 1 to 8 were 40°C, 60°C, 80°C, 115°C, 130°C, 140°C, 125°C, 110°C, respectively, and the cooling die at 35°C). The non-linear trend observed between extrusion temperature and digestibility rises the opportunity for optimisation of HME temperature profiles around C.

Additionally, after the base digestion, a plant-derived enzyme, bromelain in dose 1 mg/mL, was added to the oral phase. This was in attempt to improve the protein digestibility. Statistical analysis showed that there was no significant difference when bromelain was added, compared to those without. However, the observed trend did show a tendency for protein concentration to decrease. Hence, a higher bromelain concentration of up to 10 mg/mL is recommended for future experiments to obtain statistical significance. A texture analysis was conducted, indicating that sample C, with the highest digestibility, had the lowest toughness and firmness.

Popular Abstract

Adding pineapple juice to a plant-based diet – what is the extent of plant protein digestibility, and how can it be improved?
The worldwide consumption of plant-based alternatives is increasing for various reasons. Main reasons for consumers have been linked to environmental concern, animal welfare and land usage. In this degree project, there was collaboration with Hooked Foods, a start-up company producing plant-based fish analogues. Compared to conventional fishing, the production of plant-based fish analogues may help to reduce by-catch, habitat loss, and biodiversity decline. However, wide observation has shown that plant-based proteins are not completely digested or absorbed in the body. Common factors hindering digestion are examples such as anti-nutritional factors found in plants, interfering with nutrient absorption and, hence, reducing their nutritional value. Therefore, the investigation of plant protein digestibility is highly relevant, not only to this degree project, but also for the health benefits that will come for plant-based consumers. Especially in finding ways to improve digestibility.

The plant-based fish analogues produced by Hooked Foods, were obtained using a high moisture extrusion machine that converts proteins into fibrous structures. Specifically for this degree project, the ingredients used were microalgae protein, yellow pea protein, pea fibre, and white fish flavouring. To obtain four different samples for the digestion experiments, the latter zones of the extrusion temperatures profiles were decreased sequentially. To investigate the digestibility of the samples, the human digestive system was mimicked in the laboratory. Digestive enzymes were added for the oral, gastric, and intestinal phase, while mixing was achieved by magnetic stirrers within each glass bottle. After performing the base digestion on the samples, a plant-derived enzyme, bromelain (found in pineapple) was added to try to improve the protein breakdown. To measure the extent of digestibility, protein analysis methods were carried out to measure the protein content in the final digestates.

The results from protein analysis revealed that the four samples were significantly different to each other, meaning that the temperature profile in high moisture extrusion has an impact on protein digestibility. However, there were no significant differences between the samples containing bromelain to the samples without. However, there was an observed tendency from the averages of the replicates, that the protein digestibility does manage to increase with the addition of bromelain and higher doses for this digestive enzyme need to be tested.

• author: Heurlin, Gabriella Juliet and Jansen, Akkelien
• supervisor: Olena Prykhodko; Zhihao Peter Liu
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM02 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: high moisture extrusion, plant-based fish analogues, protein digestibility, in-vitro digestion, bromelain, food engineering, nutrition and food chemistry
• language: English
• id: 9161953
• date added to LUP: 2024-06-13 12:52:14
• date last changed: 2024-06-13 12:52:14