Abstract
As a result of population growth, an emerging middle-class, and a more health-conscious society concerned with overconsumption of fats and carbohydrates, dietary protein intake is on the rise. To address this rapid change in the food market, and the subsequent high demand for protein products, agriculture, aquaculture, and the food industry have been working actively in recent years to increase protein product output from both production and processing aspects. Dietary proteins derived from animal sources are of the highest quality, containing well-balanced profiles of essential amino acids that generally exceed those of other food sources. However, as a result of studies highlighting low production efficiency (e.g., feed to food conversion) and significant environmental impacts, together with the negative health impacts associated with the dietary intake of some animal products, especially red meats, the consumption of animal proteins has been remaining steady or even declining over the past few decades. To fill this gap, researchers and product development specialists at all levels have been working closely to discover new sources of protein, such as plant-based ingredients. In this regard, microalgae have been recognized as strategic crops, which, due to their vast biological diversity, have distinctive phenotypic traits and interactions with the environment in the production of biomass and protein, offering possibilities of production of large quantities of microalgal protein through manipulating growing systems and conditions and bioengineering technologies. Despite this, microalgae remain underexploited crops and research into their nutritional values and health benefits is in its infancy. In fact, only a small handful of microalgal species are being produced at a commercial scale for use as human food or protein supplements. This review is intended to provide an overview on microalgal protein content, its impact by environmental factors, its protein quality, and its associated evaluation methods. We also attempt to present the current challenges and future research directions, with a hope to enhance the research, product development, and commercialization, and ultimately meet the rapidly increasing market demand for high-quality protein products.
Highlights
This review focuses on the use of microalgae as human food, microalgal protein quantity, the impact of analytical methods on microalgal protein content, influence of environmental factors on microalgae protein yield, protein quality, and methods for protein quality assessment
It was reported in a review that the crude protein content in microalgae biomass ranges from 6 to 63%, where most species have over 40% crude protein content, on the basis of dry mass [39]
Protein content in Isochrysis sp. and Rhodomonas sp. decreased when they were cultivated at high temperatures in a range of 25–35 ◦ C, while protein content increased in Prymnesiophyte sp., Cryptomonas sp., and Chaetoceros sp., with the largest change occurring in Isochrysis sp. [89], in line with the results reported by others [90]
Summary
The methods and technologies conventionally used for intensifying agriculture have been very successful throughout the green revolution but are predicted to no longer be sustainable solutions soon These strategies come with high-impact trade-offs on the environment, such as the disruption of natural habitats, threats to biodiversity, climate changing GHG emissions, deforestation, desertification for livestock production, and polluting nutrient run-off from chemical fertilizers, which are damaging aquatic and terrestrial ecosystems [3,6,7]. The reasons include the following: (1) high content of protein, essential amino acids, and other healthy nutrients such as vitamins, antioxidants, omega-3 PUFAs, and minerals; (2) long-term sustainability, because microalgae have the lowest carbon, water, and arable land footprints of any crops; (3) environmental pollution remediation (e.g., ecological services); (4) high productivity compared with terrestrial crops and animal foods [1,21,22,23]. This review focuses on the use of microalgae as human food, microalgal protein quantity, the impact of analytical methods on microalgal protein content, influence of environmental factors on microalgae protein yield, protein quality, and methods for protein quality assessment
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