RESUMO: As microalgas são organismos cuja biomassa possui biomoléculas abundantes como carboidratos, lipídeos, proteínas, pigmentos, vitaminas, minerais e compostos antioxidantes, com inúmeras aplicações industriais com destaque para os segmentos de alimentos, nutricional, farmacológico, cosmético e de energia, na produção de biocombustíveis. Entretanto, o acesso de forma integra a essas biomoléculas pode ser dificultado pela rigidez estrutural de sua parede celular, sendo necessário a aplicação de um pré-tratamento que promova a lise celular. As diferentes técnicas de ruptura celular aplicáveis à biomassa microalgal descritas na literatura podem ser de natureza mecânica, com destaque para as técnicas de moagem em moinho de bolas e homogeneização à alta pressão (HAP) ou não mecânica (química, térmica e enzimática), cada uma com vantagens e desvantagens. Assim, o objetivo da presente revisão narrativa é descrever o uso de diferentes métodos para o rompimento de células de microalgas, com suas vantagens, desvantagens e seus desafios.

The high protein content of several microalgal species makes them attractive and unconventional candidates for use in the food and pharmaceutical industries. Due to the robust cell walls of microalgae, cell rupture is necessary to improve the extraction of intracellular proteins. Thus, choosing a suitable cell-breaking treatment before protein extraction is a vital downstream processing step. Additionally, it is necessary to use an effective technique for monitoring and measuring the impact of rupture treatments on microalgal cell walls. In our study, Tetradesmus obliquus cells were disrupted using three different mechanical rupture methods: high-pressure homogenization (HPH), ultrasound (US), and ball milling (BM). The ruptured biomass cells were counted, and soluble proteins were extracted and quantified. The cell-counting technique did not detect any differences between intact and damaged cells after BM treatment because the dye (erythrosine B) did not permeate the microalgal biomass accurately. The US treatment promoted the highest yield of total protein extraction (19.95%), while the highest yields in the HPH and BM treatments were 15.68% and 14.11%, respectively. Since the cell breakage method affects protein extraction from microalgal biomass, protein release can be used as a central indicator of the degree of cell disruption.

The high protein content of several microalgal species makes them attractive and unconventional for applications in the food and pharmaceutical industries. Due to microalgae's robust cell wall, cell rupture is necessary to improve the extraction of their intracellular proteins. Thus, choosing a suitable cell-breaking treatment before protein extraction is a vital downstream processing step. Additionally, it is necessary to use an effective technique for monitoring and measuring the impact of rupture treatments on microalgal cell walls. In our study, Tetradesmus obliquus cells were disrupted by three different mechanical rupture methods: high-pressure homogenization (HPH), ultrasound (US), and ball milling (BM). The ruptured biomass cells were counted, and soluble proteins were extracted and quantified. The cell counting technique did not detect differences between intact and damaged cells after BM treatment because the dye (erythrosine B) did not permeate the microalgae biomass accurately. The US treatment promoted the highest yield of total protein extraction (19.95%). The yields of protein extraction of T. obliquus with HPH (15.68%) and BM (14.11%) were significantly (p value ≤ 0.05) lower than that achieved in the US treatment. The increase in the number of extraction steps increased the protein recovery. Thus, the content of extracted soluble protein was a reliable indirect index for a quantitative comparison of the cell disruption level.

This study evaluated the effects of spray drying and freeze drying on additive-free whole milk powder in terms of physicochemical, color, techno-functional, flow, morphological, and process-efficiency properties. Three independent milk batches were processed under four spray-drying conditions defined by inlet air temperature (130 and 180 °C) and feed flow rate (0.2 and 0.8 kg/h), and one freeze-drying condition was used for comparison. Spray-dried powders showed lower moisture and water activity than freeze-dried powder, indicating greater water-removal efficiency and storage stability under the conditions evaluated. They also exhibited spherical, denser particles and narrower size distributions than the irregular, porous freeze-dried particles. In contrast, freeze-dried powder showed much faster wettability and better flowability, but also higher hygroscopicity, water activity, browning index, and drying losses, suggesting lower physicochemical stability. Among the spray-drying conditions tested, 130 °C/0.8 kg/h provided the best overall balance between stability and process efficiency, although the higher moisture variability observed for this condition indicates that additional replicates would be needed to confirm reproducibility. The 180 °C/0.8 kg/h condition produced a narrower particle-size distribution and lower moisture, but it also impaired wettability and increased mass losses.