Abstract:

The objective of this paper was to explore the effect of different drying methods i.e., spray drying, fluid bed
drying and vacuum freeze drying on the angiotensin converting enzyme (ACE) inhibitory activity of peptides from bovine
casein hydrolysate. The operating parameters were optimized to obtain both a moisture content lower than 5% and reduced
half inhibitory concentration (IC50) for ACE inhibition of dried product. The antihypertensive efficiency of the dried products
obtained by different drying methods was evaluated by animal tests. The results showed that the spray drying conditions
were optimized as 190 ℃, 75 ℃ and 44 mL/min for air inlet and air outlet temperatures and feeding rate, respectively. The
IC50 for ACE inhibition of the dried product obtained under these conditions was 0.442 mg/mL. The optimal fluid bed drying
conditions were established as 65 ℃, 180 mL and 30 g for air inlet temperature, loading amount and suspending medium
amount, respectively, which gave a dried product with an IC50 of 0.294 mg/mL for ACE inhibition. The IC50 for ACE
inhibition of the dried product obtained by vacuum freeze drying was 0.275 mg/mL. The results of animal tests showed that
upon oral administration of the three different dried products at the same dose, the anti-hypertension activity of dried product
was best maintained by by vacuum freeze drying, followed by fluid bed drying, and spray drying caused the maximum loss
of anti-hypertension activity. Therefore, vacuum freeze drying is a better drying method for casein hydrolysate rich in ACE
inhibitory peptides.

Key words: casein hydrolysate, angiotensin converting enzyme (ACE) activity inhibitory peptides, vacuum freeze drying, spray drying, fluid bed drying