Introduction: Spirulina platensis belongs to the Division of Cyanobacteria and the family of Oscillatoriaceae. It is autotroph and photo-synthesizer and can be reproduced through double cell division. Spirulina platensis is a filamentous blue-green multi-cellular microalgae naturally occurring in the tropical and alkaline lakes of America, Mexico, Asia and central Africa. It contains unique and extraordinary nutrients which can be used in the production of functional foods. Among bakery and flour products, cake has a relatively high diversity and long shelf-life and is famous among a variety of people, especially children. Since the knowledge associated with the enrichment of sponge cake, as a popular product among different communities (in particular, children) is limited, the aim of the present research is to produce a sponge cake enriched with spirulina platensis, and to examine its nutritional, physicochemical and sensory properties.
Materials and methods: In this research, the effect of Spirulina platensis at four levels (0, 0.5, 1 and 1.5%) was investigated on the nutritional properties (protein, fat, iron, zinc and copper contents), physicochemical properties (moisture content, pH, total phenol content, antioxidant potential, textural properties and color indices) and sensory attributes (odor, color, texture, flavor and taste, chewiness and total acceptance) of the sponge cake samples prepared with wheat flour.
Results and discussion: Results showed that algae powder was rich in protein (56.33%) and iron (13.18 ppm). The addition of Spirulina platensis to the sponge cake caused reduction in its moisture content during storage (days 1, 5 and 10). The results also revealed that the different levels of algae addition brought about significant differences in the moisture content of the samples (p<0.05). The results also indicated that the protein, fat and mineral contents as well as other nutritional properties of the sponge cake increased as the algae content was elevated. The total phenol content of the cake samples was also raised with an increase in the algae powder level, compared with the control. This could be attributed to the large amounts of phytochemical and biological active substances such as flavonoids, sterols and other phenolic compounds. The results demonstrated that the porosity values of the control and the sample containing 1.5% of the algae were not significantly (p<0.05) different. The percentage of porosity was equal to 24.94, 37.99, 33.39 and 27.81 in the control and the samples containing 0.5, 1 and 1.5% of Spirulina platensis. Overall, the sample with 0.5% of the algae and the control had the highest and lowest porosity percentage respectively. As the algae level rose, the textural parameters (hardness, cohesiveness and gumminess) of the sponge cake increased on days 1, 5 and 10 of the storage period. The colorimetry results showed that the effect of Spirulina platensis was significant (p<0.05) on color parameters (L*, a* and b*). Sensory evaluation revealed that the sponge cake with 0.5% of the microalgae was the most acceptable among the samples. The green color of the cake crumb was attractive to the panelists and a comparison between the total sensory scores indicated that the incorporation of Spirulina platensis into the sponge cake was desirable from the panelists` points of view. The results of this study demonstrated that the addition of Spirulina platensis to sponge cake for the enrichment of this product, caused an increase in its protein and mineral contents, antioxidant potential, in addition to other functional ingredients naturally occurring in this algae. The results revealed that different levels of this algae (0.5, 1, and 1.5%) did not significantly affect the cake texture, however, had a significant impact on its color. Incorporation of Spirulina platensis into sponge cake reduced its L*, a* and b*, which was highly noticed by the panelists. Therefore, it can be declared that enrichment of sponge cake, as a popular product among different people of societies, particularly children, is a desirable and easy way of transferring the useful and valuable compounds of this algae to human.