Determination of Biological Activities and Color Kinetics of Spirulina platensis During Convective Air Drying

Abstract

Spirulina platensis (S.platensis), procaryotic microalgae, is favored as a functional food owing to the high protein content, fatty acid, phenolics, vitamins, and minerals preferred by consumers. Producers prefer to sell it in dry form because of the shipping and shelf-life advantages. This study intends to describe the effect of convective drying on biological activities and color changes of S.platensis. Firstly, mass production of S. platensis was accomplished in flat-panel bioreactor, and harvested cells were dried by a convective hot air dryer. Convective drying treatments were carried out at 40, 45, and 50 °C. On the contrary of the total phenolic content values, an increase in the temperature from 45ºC to 50 ºC was more effective than the increase from 40 ºC to 45 ºC on the antioxidant capacity of the samples. Activation energy values were calculated for the antioxidant capacity and total phenolic content were about 24.46 kJmol-1 and 24.94 kJmol-1, respectively. The color values (L, a, b) were measured, and the total color difference (ΔE) was calculated as 3.019, 2.98, and 2.94 at 40, 45, and 50°C, respectively. ΔE characterized by a zero-order model and the activation energy (Ea) for change in ΔE was calculated as 50.15 kJ.mol-1. The results indicated that the most suitable temperature most suitable temperature for convective drying for S.platensis would be nearly 50°C.

Keywords

• Antioxidant capacity
• convective drying
• drying and color kinetics
• Spirulina platensis
• total phenolic content.

Konvektif Kurutma Süresince Spirulina platensis'in Renk Kinetiği ve Biyolojik Aktivitelerinin Belirlenmesi

Öz

Prokaryotik bir mikroalg olan Spirulina platensis (S.platensis), yüksek protein içeriği, yağ asidi, fenolikler, vitaminler ve mineraller nedeniyle tüketiciler tarafından fonksiyonel gıda olarak tercih edilmektedir. Üreticiler ise nakliye ve raf ömrü avantajları nedeniyle S.platensis’in kurutularak satışa sunulmasını arzu etmektedir. Bu çalışma ile kurutma metotlarından biri olan konvektif kurutmanın S.platensis'in biyolojik aktivitesi ve renk değişikliği üzerindeki etkisi incelenmiştir. Öncelikle panel biyoreaktörde S.platensis'in üretimi gerçekleştirilmiştir ve hasat edilen aynı biyokütleye sahip hücreler konvektif sıcak hava kurutucusu ile kurutulmuştur. Konvektif kurutma işlemleri 40, 45 ve 50 °C' de gerçekleştirilmiştir. Sıcaklığın 45 ºC' den 50 ºC' ye kadar olan artışı antioksidan kapasitesi üzerinde etkili olurken 40 ºC' den 45 ºC' ye yükseltilmesi toplam fenolik içerik değerleri üzerinde etkili olmuştur. Antioksidan kapasite ve toplam fenolik içerik için hesaplanan aktivasyon enerjisi değerleri sırasıyla 24.46 kJmol-1 ve 24.94 kJmol-1 olarak hesaplanmıştır. Renk değerleri (L, a, b) ölçülmüş ve 40, 45 ve 50 °C' deki toplam renk farkı (ΔE) sırasıyla 3.019, 2.98 ve 2.94 olarak hesaplanmıştır. ΔE sıfır dereceli bir model ile karakterize edilmiştir ve ΔE' deki değişim için aktivasyon enerjisi (Ea) 50.15 kJ.mol-1 olarak hesaplanmıştır. Sonuçlar en etkin kurutma sıcaklığının 50 °C olduğunu göstermiştir.

Anahtar Kelimeler

• Antioksidan kapasitesi
• konvektif kurutma
• kurutma ve renk kinetiği
• Spirulina platensis
• toplam fenol içeriği.

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