Effect of Pulsed Electric Field (PEF) on Bacterial Viability and Whey Protein in the Processing of Raw Milk

Effect of pulsed electric field treated on quality of curd

Pulsed electric field (PEF) is a potential pre-treatment technique to improve the quality of milk by reducing its microbial load. The present study aims at addressing this issue with respect to a popular fermented dairy product, that is, curd. Milk was treated with high voltage and frequency (55 kV and 90 Hz) square waves of pulse width 900 µs for 100 s. Curd samples were prepared with conventional heat treatment (CHT), PEF-treated milk subjected to CHT (PT-CHT), and PEF-treated milk (PT). PT samples resulted in curd with higher acidity (0.17 ± 0.005% LA) and microbial load (6.65 ± 0.27 log CFUg-1), while the PT-CHT samples resulted in curd with better whey holding capacity. The firmness recorded for CHT, PT-CHT, and PT was 1.15 ± 0.05, 1.32 ± 0.04, and 0.91 ± 0.03 N, respectively. PT-CHT showed a higher viscosity index, that is, 0.207 ± 0.005 g. Sensorial properties showed the acidic nature of PT-curd with greater syneresis and softer texture resulted in its poorer sensory scores for texture. Shelf-life analysis showed no significant difference between curd prepared using the CH and PT-CHT up to 12 days. The study demonstrated the potential of employing PEF with CHT for improving the texture and shelf life of curd without impacting its quality.

Impact of Electric Arcs and Pulsed Electric Fields on the Functional Properties of Beta-Lactoglobulin

Beta-lactoglobulin (β-lg) is a major whey protein with various techno-functional properties that can be improved by several treatments. Therefore, the objective of this study was to explore the impact of green high-voltage electrical treatments (HVETs)—namely, pulsed electric fields and electric arcs—on the functional properties of β-lg. Both emulsifying and foaming stability and capacity, as well as the hygroscopicity of non-treated and pretreated β-lg, were explored. The results demonstrated that the emulsifying capacity and stability of pretreated samples increased by 43% and 22% when compared to native β-lg, respectively. Likewise, the pretreated β-lg displayed better foaming stability compared to native β-lg. In addition, the HVETs significantly decreased the hygroscopicity of β-lg (by 48% on average), making it a good ingredient with reduced hygroscopicity for the food industry.

Reversible Electroporation and Post-Electroporation Resting of Thai Basil Leaves Prior to Convective and Vacuum Drying

Pretreatment by reversible electroporation followed by resting (storage under saturated moisture at 21 ± 2 °C) was evaluated for modification of the properties of dried and rehydrated Thai basil leaves. The treated leaves were dried by convection at 40 °C or in a vacuum at room temperature. The results showed that vacuum drying provoked more cell damage and tissue collapse than convective air drying at a moisture ratio (MR) of 0.2 and 0.1. Under this level of MR, the pulsed electric field (PEF) and resting pretreatment exerts a protective effect of the tissue for both drying methods. However, under complete dehydration (water activity, aw = 0.05) damage seems to be similar for both drying methods despite the PEF pretreatment. Remarkably, reversible electroporation followed by resting resulted in higher trichome preservation. At MR of 0.05, the area of trichomes on the surface of convective-dried, PEF-rested and fresh samples were not statistically different at 2267 ± 89 µm2 and 2218 ± 65 µm2, respectively, showing that this pretreatment still exerts a protective effect on trichomes when complete dehydration is achieved.