Freeze-Dried Tuna Pepsin Powder Stabilized by Some Cryoprotectants: In Vitro Simulated Gastric Digestion toward Different Proteins and Its Storage Stability

The impact of maltodextrin (10%) in combination with trehalose or glycerol at different levels (2.5% and 5%) and their mixture on the stability of freeze-dried pepsin from skipjack tuna stomach was studied. Addition of 5% trehalose and 10% maltodextrin yielded the powder (TPP-T5) with highest relative pepsin activity (p < 0.05). TPP-T5 had different shapes and sizes, with mean particle size of 65.42 +/- 57.60 mu m, poly-dispersity index of 0.474, and zeta potential of -19.95. It had bulk density of 0.53 kg M-3 and possessed fair flowability. The wetting time for TPP-T5 was 16.36 +/- 0.73 min, and solubility was 93.58%. TPP-T5 stored at room temperature under different relative humidities could maintain proteolytic activity up to 4 weeks. Commercial porcine pepsin (CP) and crude tuna pepsinogen had molecular weights of 35.2 and 43.3 kDa, respectively, when analyzed using gel filtration (Sephadex G-50) and SDS-PAGE. Tuna pepsin had comparable hydrolysis toward threadfin bream muscle protein, whey protein isolate, and kidney bean protein isolate to commercial pepsin, especially at a higher level (15 units/g protein). Digested proteins contained peptides with varying molecular weights as determined by MALDI-TOF. Therefore, pepsin from skipjack tuna stomach could replace commercial porcine pepsin and was beneficial supplement for patients with maldigestion, particularly the elderly.

Automated summary

The study investigated the impact of maltodextrin and combinations of trehalose or glycerol on the stability of freeze-dried pepsin from skipjack tuna stomach. The results showed that the addition of 5% trehalose and 10% maltodextrin yielded the powder with the highest relative pepsin activity. The powder exhibited good flowability, solubility, and could maintain proteolytic activity under different humidity conditions.