Effects of High-Pressure, Microbial Transglutaminase and Glucono-δ-Lactone on the Aggregation Properties of Skim Milk

Abstract

The object in this study is to investigate the effects of high pressure and freezing processes on the curdling of skim milk depending on the presence of transglutaminase (TGase) and glucono-δ-lactone (GdL). Skim milk was treated with atmospheric freezing (AF), high pressure (HP), pressure-shift freezing (PSF) and high pressure sub-zero temperature (HPST) processing conditions. After freezing and pressure processing, these processed milk samples were treated with curdling agents, such as TGase and GdL. Pressurized samples (HP, PSF and HPST) had lower lightness than that of the control. In particular, PSF had the lowest lightness (p<0.05). Likewise, the PSF proteins were the most insoluble regardless of whether they were activated by TGase and GdL, indicating the highest rate of protein aggregation (p<0.05). Furthermore, the TGase/GdL reaction resulted in thick bands corresponding to masses larger than 69 kDa, indicating curdling. Casein bands were the weakest in PSF-treated milk, revealing that casein was prone to protein aggregation. PSF also had the highest G' value among all treatments after activation by TGase, implying that PSF formed the hardest curd. However, adding GdL decreased the G' values of the samples except HPST-treated samples. Synthetically, the PSF process was advantageous for curdling of skim milk.

Applications of High Pressure Technology in Food Processing

“…The optical parameter L* (lightness) of milk exposed to 100-200 MPa slightly differed from the untreated sample whereas those treated at 200-400 MPa saw a progressive reduction (Huppertz, Fox & Kelly, 2004;Huppertz, Kelly & de Kruif, 2006;Needs, Stenning, Gill, Ferragut & Rich, 2000). HP treated skim milk at 200 MPa at 4 o C was found to decrease L* values (Lee, Choi, Cho & Davaatseren, 2016). Harte, Luedecke, Swanson and Barbosa-Canovas (2003) reported that milk reduced its white colour and changed to yellow when the sample was subjected to thermal treatment followed by high pressure processing (300-676 MPa) but regained its white colour when the sample was exposed to HPP followed by thermal processing.…”

Effects of High Hydrostatic Pressure on Technical Functional Properties of Edible Insect Protein

“…Non-thermal, high pressure processing is a well-known, effective, and eco-friendly method to improve extract yield (Chen et al, 2010). High pressure technology instantly and uniformly transfers pressure to a sample using oil as a pressure medium at 100-500 MPa (Lee et al, 2016).…”

“…Non-thermal, high pressure processing is a well-known, effective, and eco-friendly method to improve extract yield ( Chen et al, 2010 ). High pressure technology instantly and uniformly transfers pressure to a sample using oil as a pressure medium at 100–500 MPa ( Lee et al, 2016 ). High pressure affects sterilization and extraction by causing a change in the physical biochemical environment of the sample ( Farkas and Hoover, 2000 ).…”