Effect of ultra-high pressure homogenization and heat treatment on physicochemical properties of almond beverage

摘要

The effect of ultra-high pressure homogenization (UHPH) and conventional heat treatments (HT) onphysicochemical properties of almond beverage was studied. Almond beverage base product (BP) wasproduced by soaking and grinding Marcona almonds. The milky liquid obtained was pre-homogenized byusing a vacuum rotor-stator system and afterwards homogenized with a high pressure homogenizer byapplying 62, 103 and 172 MPa. In samples submitted to HT, 85 °C/30 min or 121 °C/15 min conditions wereused prior to the homogenization step. Physicochemical characterization was carried out in BP and insamples submitted to HT and UHPH throughout the determination of the rheological behavior, colorparameters, particle size distribution, ζ-potential and thermal analysis. Results showed that physicochemicalproperties of the product were severely modified by HT and also by UHPH in lesser extent. PB samples andthose processed with the lowest homogenization pressure showed a bimodal and polydisperse distribution.Samples treated with the higher homogenization pressures (103 and 172 MPa) evidenced a significantreduction of particle size and clusters’ deflocculation, leading to a monodisperse distributions. The HTcaused an increment of particle size due to coagulation phenomena, this effect being more intense whenusing higher temperatures. ζ-potential was especially lowered in samples submitted to both thermal andUHPH treatments, leading to lower electrically charged particles. Color differences between BP, UHPH andHT samples were found. Thermal treatments led to a notable decrease (p<0.05) in the luminosity of samples.Nevertheless, this negative effect was diminished when these samples were ultra-homogenized. BP showed aNewtonian behavior and UHPH and HT decreased the flow index parameter, thus showing a shear thinningbehavior (n<1). The viscosity of the treated samples (HT or UHPH) increased, although the differencesbetween BP and UHPH were low. The analysis of DSC thermograms from different samples revealed thatthe homogenization pressures used were not high enough to affect the denaturalization pattern of proteins.