Effects of Microwave and Ultrasound Assisted Extraction on the Recovery of Soy Proteins for Soy Allergen Detection

Abstract

The extraction of soy proteins for soy allergen detections is conventionally achieved with PBS buffer for at least 2 h at room temperature or 4 °C. This method has been reported to be inefficient due to time consumption and inadequate protein extraction resulting in false negative allergen detection and mislabeling of foods containing allergenic proteins. This study investigated the application of microwave (MAE) and ultrasound assisted extraction (UAE) techniques to extract and improve recovery of allergens from various soy matrices. Soy proteins were extracted from raw soy flour, soy protein isolate (SPI) and soy milk using MAE at 60, 70, and 100 °C for 5 and 10 min and UAE at 4 and 23 °C for extraction times of 1, 5, and 10 min with PBS, Laemmli and urea buffers. Extracts were analyzed for total proteins, protein profile, and antibody-based detection (ELISA) of soy proteins. Conventional extraction with each of the buffers was used as controls. Overall, proteins recovered from MAE and UAE samples were higher than recoveries from the controls in all soy matrices. Under all extraction conditions, Laemmli and urea buffer recovered more proteins than PBS. Electrophoresis analysis of protein showed bands around 75, 50, and 33 kDa indicating the presence of soy allergenic proteins β-conglycinin and glycinin, in all samples. Using sandwich ELISA, control and UAE extracts resulted in high soy protein detection but this reduced in MAE extracts.

Evaluation of the efficiency of three extraction conditions for the immunochemical detection of allergenic soy proteins in different food matrices

“…In a recent study, Amponsah and Nayak compared the effects of different extraction buffers and conditions on soy protein extraction. They studied Laemmli buffer at pH 6.8 as one of the extraction buffers and concluded that it was effective in improving soy protein recovery.…”

“…According to the investigators, the presence of the detergent SDS in Laemmli buffer may have resulted in its ability to recover high protein yields compared with the conventional extraction buffer PBS. The use of UAE has also been studied by several investigators who have reported it to be an efficient extraction method , , , . For instance, Albillos et al .…”

“…The protein profile of each commercial and in‐house sample was determined by separating its proteins . This was achieved by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) using a Mini‐PROTEAN ® Tetra cell (Cat # 165‐8004, Bio‐Rad, Hercules, CA, USA).…”

“…also improved the solubility of soy protein concentrate (SPC) by treating SPC dispersed in water with ultrasound 20 kHz probe and ultrasound bath (40 and 500 kHz) systems. Amponsah and Nayak investigated the effect of microwave‐ and ultrasound‐assisted extraction (MAE and UAE) in combination with different extraction buffers on soy protein solubility for improved soy allergen detection. In their study, soluble proteins were extracted from samples of soy flour, soy protein isolate and soy milk dispersed in PBS, Laemmli buffer or urea using conventional extraction, UAE and MAE.…”

“…Under all extraction conditions, Laemmli buffer and urea recovered more proteins than the conventional PBS. Immunological analysis using sandwich enzyme‐linked immunosorbent assay (ELISA) showed high soy protein detection in extracts from conventional extraction and UAE …”