Effects of Growth Medium Variation on the Nutri-Functional Properties of Microalgae Used for the Enrichment of Ricotta
1University of Carthage, INSAT, Laboratory of Protein Engineering and Bioactive Molecules (LR11ES24), BP 676, 1080, Cedex, Tunisia
2University of Carthage, Higher Institute of Fisheries and Aquaculture, BP 15, Errimel, 7080, Bizerte, Tunisia
Received: 20 December 2020
Accepted: 12 November 2021
Nannochloropsis gaditana; Chlorella sp.; ricotta cheese; growth media; antioxidant; nutritional profile; sensory evaluation
Research background. Microalgae represent an emergent sustainable source of bioactive compounds such as antioxidants, vitamins, minerals, and polyunsaturated fatty acids that can ameliorate the nutritional characteristics of foods. The biochemical composition of microalgae could be modulated by varying the culture conditions to enhance the accumulation of biomolecules of interest. The aim of this work is to optimise the nutri-functional properties of two microalgae with potential utility for food-application.
Experimental approach. Nannochloropsis gaditana L2 and Chlorella sp. SM1 were screened for growth, biochemical composition, and radical scavenging activity employing four different growth media (algal, BG-11, f/2, and Conway) with different nutrients composition. Additionally, the feasibility of using Chlorella sp. SM1 cultivated in BG-11 medium, in a Mediterranean under-investigated dairy product, ricotta cheese, and its effect on the sensory attributes was investigated.
Results and conclusions. Nitrate- and phosphate-rich media (BG-11 and algal) enhanced the biomass productivity. However, the highest lipid productivity (23.10 mg/(L·day), 11.86 mg/(L·day) for SM1 and L2 respectively) and carbohydrate content (34.79 and 44.84 % for SM1 and L2 respectively) were obtained with the nitrate-deficient f/2 medium. Regardless of the used medium, the lipidic profile of Chlorella sp. SM1 and Nannochloropsis gaditana L2 remained adequate for different applications with the presence of C16-18 as main fatty acid (>50 %). Significant increase in oleic acid (C18:1) content was recorded in response to nitrogen deficiency, being the highest in SM1 in f/2 medium (34 %). Nitrogen deficiency was also found to enhance phenolic compounds (48.8 and 35.1 GAE/(mg/g) for SM1 and L2 respectively) and carotenoids contents (2.2 and 2 mg/g for SM1 and L2 respectively). Due to its interesting antioxidant potential, Chlorella sp. SM1 was used to enrich the ricotta cheese product at different concentrations (0.2, 1 and 1.5 %). The sample with 0.2 % was found to give the most appreciated product.
Novelty and scientific contribution. This study permitted the production of an innovative ricotta cheese using Chlorella as a functional ingredient, without altering the manufacturing diagram while maintaining acceptable sensorial characteristics. The biochemical composition of the used strains varied depending on the culture medium composition, which permitted the accumulation of phytonutrients of interest.