Evaluation of Microbiological Safety and pH Stability of Autoclaved Pea Protein Beverages

Post-thermally treated, all beverages exhibited high microbiological safety. However, their stability during storage varied with composition, processing parameters, and temperatures. Refrigerated storage at 5 °C preserved microbiological stability, while room temperature storage at 22 °C resulted in yeast and mold growth in certain formulations, particularly when subjected to lower intensity treatments (105-110 °C). Treatment at 115 °C consistently ensured complete microbiological stability. Throughout the investigation, pH values remained stable, indicating overall chemical stability. The findings suggest that the interplay between beverage composition, acidity, and thermal processing significantly influences microbiological stability in pea protein isolate beverages.

Introduction: Pea protein isolate is gaining traction as a sustainable, high-quality plant-based protein source, particularly within the European Union, where pea production exceeded 2 million tons in 2018. The rising demand for sustainable proteins aligns with the global trend towards plant-based food products. With a protein content of approximately 80-85%, pea protein isolate is well-regarded for both its nutritional value and functional properties. While substantial raw material input is needed for production, the sustainability of pea protein is supported by its minimal impact on arable land and various agronomic advantages such as low water requirements.

Pea protein isolate is produced through wet fractionation, reducing antinutrients and enhancing solubility. Environmental pH significantly affects its functional properties, as solubility decreases near the isoelectric point (pH 4.5-5.0). Combining pea protein isolate with other plant components can create nutritionally balanced food products. pH levels largely depend on the organic acids from fruit juices used in beverages, which naturally promote acidity and microbiological stability.

Thermal treatments, specifically autoclaving, are critical in ensuring microbiological safety. The effective inactivation of microorganisms, including spores, can be achieved at temperatures of 105-115 °C without significant detriment to nutritional quality. This study aimed to evaluate how different thermal processing conditions affect the microbiological safety and pH stability of preservative-free pea protein isolate beverages.

Materials and Methods: Five beverage variants were created, including lemon, pomegranate-cranberry, blueberry-vanilla, blueberry-lemon, and blackcurrant-apple. Each contained pea protein isolate as the primary ingredient, complemented by various fruit juices. The beverages were subjected to thermal processing using a laboratory-scale autoclave with variations in temperature and exposure time, followed by microbiological analyses conducted immediately after treatment and after storage.

Results indicated that, for instance, the blackcurrant-apple beverage stayed below the regulatory microbiological limits immediately after processing. However, certain samples exhibited higher counts after storage at room temperature, highlighting the impact of both temperature and treatment intensity on microbial stability and growth. The pH levels of the beverages remained stable throughout the study, affirming the effectiveness of the processed conditions.

Discussion observed differences in microbiological profiles across beverages, linked closely to their compositions and thermal treatments. For example, the blueberry-lemon beverage maintained low counts, but variations occurred due to its specific formulation. Additionally, while acidic environments effectively inhibit bacterial growth, yeast growth was noted under certain storage conditions, particularly at elevated temperatures.

In conclusion, the study suggests that pea protein isolate beverages can maintain microbiological stability through moderate thermal processing and acidic formulations, supporting the development of clean-label, preservative-free products. Further research is needed on extended storage impacts and profiling specific microbial species responsible for spoilage, which could enhance the understanding of beverage stability in real-world scenarios.