Factors affecting the inactivation of the natural microbiota of milk processed by pulsed electric fields and cross-flow microfiltration

Abstract

Prior to processing milk and cream were standardised and homogenised. Skim milk was cross-flow microfiltered (CFMF) prior to treatment with pulsed electric fields (PEF) or high temperature short time (HTST) pasteurization. The effect of temperature of the skim milk and product composition on the efficacy of PEF treatment was determined. The electrical conductivity of the product was related to fat and solids content and increased 5% for every g/kg increase of solids and decreased by nearly 0·7% for every g/kg increase of fat. From the three microbial groups analyzed (mesophilic, coliform, and psychrotroph) in milks differences (P<0·05) in the inactivation of mesophilic microorganisms were observed between the counts following PEF treatment, while HTST pasteurization resulted in higher reductions in all different counts than those obtained after PEF. Increasing the skim milk temperature prior to PEF treatment to about 34°C showed equivalent reductions in microbial counts to skim milk treated at 6°C in half the time. The reductions achieved by a combination of CFMF and PEF treatments were comparable to those achieved when CFMF was combined with HTST pasteurization. A higher reduction in coliform counts was observed in homogenised products subjected to PEF than in products that were only standardised for fat content.

Performance of Electrode Materials During Food Processing by Pulsed Electric Fields

“…2(b). Due to the high electrical conductivity of the liquid food products [15], [16], the processing chamber acts as a purely resistive load. As a result, the transient current would be expected to follow first-order behavior during the capacitor discharge.…”

Uso de microfiltração para melhoria da qualidade e extensão da vida de prateleira de leite pasteurizado

“…A microfiltração também tem sido utilizada em combinação com o processo de pulsos elétricos e se conseguiu uma redução de microrganismos mesófilos maior que 4,0 ciclos log, comparável ao processo de microfiltração seguido de pasteurização (RODRÍGUES-GONZÁLEZ et al, 2011).…”

Change in Color and Volatile Composition of Skim Milk Processed with Pulsed Electric Field and Microfiltration Treatments or Heat Pasteurization

“…Commercially available thermal processing methods promise a high degree of microbial safety but can adversely affect other food properties such as color and volatile compounds. Several studies have demonstrated a comparable impact of PEF and MF processes on microbial inactivation in foods [ 13 , 14 , 15 , 16 , 17 ]. Milk has its natural color due to the reflectance of light by dispersed milk fat globules, proteins, and natural milk pigments like riboflavin and carotenoids [ 18 , 19 ].…”

“…Microfiltration is one of the non-thermal technologies that have been commercially allowed for extending shelf life of milk, although its use as a stand-alone treatment is restricted due to regulatory requirements [ 25 ]. Based on microbiological data, previous studies have indicated that the safety of skim milk processed with a combination of PEF and MF is comparable to that achieved by HTST pasteurization [ 13 , 17 ], potentially representing a non-thermal alternative to the well-established heat pasteurization. However, the effect of this novel process on color and volatile compounds has not been determined.…”