Adaptation and evaluation of performance of aseptic system for fluid milk in plastic bottle

Author(s)

Rodrigo Rodrigues Petrus

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2004-12-17

Examining board members

José de Assis Fonseca Faria; Mauro Faber de Freitas Leitão; Carlos Alberto Rodrigues Anjos; Arnaldo Yoshiteru Kuaye; Helena Maria André Bolini; Salvador Massaguer Roig; Pilar Rodriguez de Massaguer

• Advisor: José de Assis Fonseca Faria

Abstract

The objective of this research was the adaptation and performance evaluation of a pilot aseptic system for liquid milk filled into plastic bottles. The system was evaluated by identifying and systematically monitoring the process control points, by commercial sterility tests, sensory, physical and chemical analyses of the product and an evaluation of the packaging. The control points were monitored before and during process as follows: heat treatment of the milk; operational conformity during filling in the aseptic room including pressurization, air movement rate, total and viable particle count and evaluation of surface cleanliness and sanitation; microbiological analyses of the rinsing waters used in the process and filling lines and an analysis of the packages and their rinsing water. Four 150L batches of milk with pH values of about 6.7 were heat processed between 135 and 144°C for 10s in a plate heat exchanger and filled aseptically into 500mL high density polyethylene (HDPE) bottles in an ISO class 7 clean room. The aseptic condition of the bottles was obtained by spraying with a mixture containing 0.5% peracetic acid and 0.8% hydrogen peroxide for 10s at 30°C. The processed milk using the pilot aseptic system was compared by sensory analysis with commercial long life milk filled into carton-type packages and plastic bottles. The results of the microbial evaluation of the control points indicated good performance of the system developed based on the low counts and absence of microorganisms at some evaluated points. Of the 4 batches processed, 2 attained commercial sterility based on the physical-chemical and microbiological criteria adopted. The shelf life of the product, estimated according to the sensory tests, was 4 weeks for the first two batches processed, 8 for batch 3 and 11 for batch 4. The opacity of the packaging used was 90%, lower than that of commercial packaging, which was 100%. Thus the light barrier property was considered inadequate considering the high sensitivity of milk to the photooxidation. It was concluded that the pilot aseptic system evaluated corresponded to the performance expectations, however, it should be submitted to some implementations of improvements in its infrastructure in order to be recommended for small-scale commercially ile milk production (AU)