Comparing different dehydration methods on protein quality of krill (Euphausia Pacifica)

Abstract

Krill, (Euphausia pacifica) contains a high protein content (>15.4%) and an estimated biological value higher than many animal protein sources. Thus it is considered to be an important source of high-quality protein. However, commercial processing of krill is limited due to problems such as presence of hydrolytic enzymes (proteases, carboxypeptidases, nucleases, and phospholipases), and its small size. These enzymes are released immediately upon krill harvesting, resulting in autolysis, and rapid spoilage. Herein we compared different dehydration methods of krill on its protein quality. We processed Krill using air-drying (AD), vacuum microwave drying at low temperature (VD) and freeze-drying (FD), and also treated krill with chitinase prior to drying (HZ). AD-processed krill displayed the lowest in-vitro digestibility (P < 0.05) along with low apparent in-vivo protein digestibility compared to VD and FD, respectively. This result corresponded to lower available lysine in AD dried krill (5.6 mg/100 mg protein) compared to VD (8.5 mg Lysine /100 mg protein), FD (8.5 mg/100 mg protein), and HZ (8.9 mg/100 mg protein). Using a two-week metabolic study with rats, we found that apparent urinary nitrogen losses and net protein utilization were low in krill, compared to a casein control. The addition of chitinase to krill prior to drying significantly increased protein quality measures. A high fluoride concentration was also detected in dehydrated krill, irrespective of the drying method. It is expected that the fluoride content of krill is an additional factor that will affect protein utilization.

Keywords: Dehydration technologies; Fluoride; Freeze drying; Krill; Protein quality; Vacuum drying.