Characterization of partially purified milk-clotting enzyme from sunflower (Helianthus annuus) seeds.

Assia I A M Nasr,Omer I A Hamid,Isam A Mohamed Ahmed

doi:10.1002/fsn3.338

Assia I A M Nasr, Omer I A Hamid + Show 1 more

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https://doi.org/10.1002/fsn3.338

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Abstract

This study was aimed to extract milk‐clotting enzyme from sunflower seeds and to determine its potentiality for manufacturing white soft cheese from cows and goats milk. The seeds were blended and extracted using two types of buffers and milk‐clotting and proteolytic activities were evaluated. The enzyme was partially purified using ammonium sulfate fractionation techniques. Results indicated that sunflower seeds extracted with 5% NaCl in 50 mmol/L acetate buffer, pH 5.0, had the highest milk‐clotting activity (MCA) and lowest coagulation time compared to that extracted with only acetate buffer (pH 5.0). Ammonium sulfate at 30–50% saturation purified the enzyme to 4.3 folds with MCA of 241.0 U/mL and final enzyme yield of 10.9%. The partially purified enzyme was characterized by SDS–PAGE that showed two bands with molecular weight of 120 and 62 kDa. When compared with other plant enzymes, the partially purified sunflower enzyme was found to have higher milk‐clotting activity and lower proteolytic activity. Also, both milk sources and enzyme types significantly affected the cheese yield and curd formation time. The cheese made from cow milk using sunflower enzyme had higher yield compared to that obtained using commercial rennet, whereas the opposite was observed when using goat milk.

Highlights

Milk clotting is the basic step in the manufacture of all types of cheeses and based on that all cheese varieties (>2000 types) are classified into three superfamilies those include rennet coagulated, acid coagulated, and a combination of heat and acid coagulated cheeses (Badgujar and Mahajan 2014; Fox et al 2015)
The preliminary experiments (Table 1) showed that sunflower seeds extracted with 5% NaCl in 50 mmol/L sodium acetate buffer, pH 5.0, had significantly (P ≤ 0.05) higher milk-clotting activity compared to that extracted with the
The results showed that the 30-50% ammonium sulfate saturation fraction had the highest milk- clotting activity compared to other fractions

Summary

Introduction

Milk clotting is the basic step in the manufacture of all types of cheeses and based on that all cheese varieties (>2000 types) are classified into three superfamilies those include rennet coagulated, acid coagulated, and a combination of heat and acid coagulated cheeses (Badgujar and Mahajan 2014; Fox et al 2015). Rennet coagulated cheese represent the major type (~75%) and calf rennet has been and still the most widely used milk-clotting enzyme preparation in cheese making industry (Mohamed Ahmed et al 2009a). In the last decades there has been increased demand for cheese production and consumption due to the population explosion (Elsamani et al 2014; Tajalsir et al 2014). This combined with the elevated price of calf rennet and reduced quantity of natural calf rennet (Mohamed Ahmed et al 2010). All the above reasons have demanded the search for a new enzyme with a high ratio of milk-clotting/proteolytic activity and low preparation

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