Impact of pulsed electric fields pre-treatments on the Isoflavone profile of soymilk

In this study, pulsed electric fields (PEFs) were evaluated as extraction-aiding technology during soymilk manufacturing to improve its isoflavone profile. Low-intensity PEFs were applied at different processing conditions in two stages of the soymilk extraction process, hydrated soybeans (HSB) and soybean slurry (SBS), with the soymilk extracted from the conventional process as control (CSM). Overall, resultant soymilk samples from PEF-HSB and PEF-SBS presented lower concentrations of glucosides isoflavones and greater aglycone content than those in CSM. In contrast to genistin (Gin) and daidzin (Din), which decreased around 18.5-52.6% and 10.9-54.6%, respectively, an increase in genistein (Ge, 12.3-64.4%) and daidzein (Da, 9-55.8%) was observed. The total isoflavone content (TIC) of most soymilk samples prepared from PEF-HSB was lower than that of the CSM. Conversely, when PEF-SBS was used, the TIC of resultant soymilk was not significantly affected or slightly decreased. However, PEF treated HSB at 10 kVcm−1/100 pulses and SBS at 6 kVcm−1/10 pulses led to a significant augment in TIC, of up to 109 ± 2.39 and 110 ± 1.26 μg/g, respectively, in the extracted soymilk samples. These results indicated that low-intensity PEF is a potential technology that could be implemented during soymilk manufacturing processing to modify the isoflavone profile and content of soymilk, mainly increasing its aglycone concentrationThis research was funded by Tecnologico de Monterrey and the University of Lleida with research funds of FUNFOODEMERTEC Project

Effect of Pulsed Electric Fields (PEF) on Extraction Yield and Stability of Oil Obtained from Dry Pecan Nuts (Carya illinoinensis (Wangenh. K. Koch))

Pulsed electric fields (PEF) have been reported to increase the total oil extraction yield (OEYTOTAL) of fresh pecan nuts maintaining oil characteristics and increasing phenolic compounds in the remaining by-product. However, there is no information regarding the PEF effect on dry pecan nuts. Dry kernels were pretreated at three specific energy inputs (0.8, 7.8 and 15.0 kJ/kg) and compared against untreated kernels and kernels soaked at 3, 20 and 35 min. OEYTOTAL, kernels microstructure, oil stability (acidity, antioxidant capacity (AC), oil stability index, phytosterols and lipoxygenase activity), along with by-products phenolic compounds (total phenolics (TP), condensed tannins (CT)) and AC were evaluated. Untreated kernels yielded 88.7 ± 3.0%, whereas OEYTOTAL of soaked and PEF-treated kernels were 76.5–83.0 and 79.8–85.0%, respectively. Kernels microstructural analysis evidenced that the 0.8 kJ/kg pretreatment induced oleosomes fusion, while no differences were observed in the stability of extracted oils. PEF applied at 0.8 kJ/kg also increased by-products CT by 27.0–43.5% and AC by 21.8–24.3% compared to soaked and untreated kernels. These results showed that PEF does not improve OEYTOTAL when it is applied to dry pecan nuts, demonstrating that kernelsʹ moisture, oil content and microstructure play an important role in the effectiveness of PEF.This research was funded by Tecnológico de Monterrey and Consejo Nacional de Ciencia y Tecnología (CONACyT) scholarship programs (CVU 418204)

High-pressure Processing: Kinetic Models for Microbial and Enzyme Inactivation

High pressure processing (HPP) has become the most widely accepted nonthermal food preservation technology. The pressure range for commercial processes is typically around 100-600 MPa, whereas moderate temperature (up to 65°C) may be used to increase microbial and enzymatic inactivation levels. However, these industrial processing conditions are insufficient to achieve sterilization since much higher pressure levels (>1000 MPa) would be required to inactivate bacterial endospores and enzymes of importance in food preservation. The next generation of commercial pressure processing units will operate at about 90-120°C and 600-800 MPa for treatments defined as Pressure Assisted Thermal Processing (PATP), or Pressure Assisted Thermal Sterilization (PATS) if the commercial food sterilization level required is achieved. Most published HPP kinetic studies have focused only on pressure effects on the microbial load and enzyme activity in foods and model systems. Published work on primary and secondary models to predict simultaneously the effect of pressure and temperature on microbial and enzymatic inactivation kinetics is still incomplete. Moreover, few references provide a detailed and complete analysis of theoretical, empirical, and semi-empirical basis for the kinetic models proposed to predict the level of microbial and enzyme inactivation achieved. This review organizes these published kinetic models according to the approach used, and then presents an in-depth and critical revision to define the modeling research needed to provide commercial users with the computational tools needed to develop and optimize pasteurization and sterilization pressure treatments.Keywords: Primary and Secondary Models, High Pressure Processing, Kinetics, Microbial Inactivation, Pressure Assisted Thermal Processing, Enzyme Inactivatio