Fruit Juice Pasteurization

Abstract

Abstract

Fresh apples and pears are a good sourcer of antioxidants, fiber and vitamin C and for juice processors it is of importance to maintain them during their processing and shelf-life. Moreover, its microbial safety and stability should be guaranteed. For this reason, several research has been carried out to optimize juice processing in order to avoid undesirable quality changes, increase yield production and ensure microbial safety. In this chapter, conventional processing techniques are explained and compared to innovative technologies. The effect of novel and conventional thermal methods (pasteurization and HTST) on the nutritional content, quality-related enzymes, microbial inactivation and organoleptic attributes is described.

Alicyclobacillus acidoterrestris is acidophilic spore-forming, heat-resistant organism that may be found in fruit juices. This microorganism can survive commercial pasteurization processes commonly applied to apple and pear juices spoiling fruit juice by producing cloud loss, development of off-flavours, CO2 production or changes in color and appearance (Lawlor et al. 2009). Saritas et al. (2011) evaluated the effect of ascorbic and cinnamic acid addition and different pasteurization parameters on the inactivation of A. acidoterrestris. They concluded that the increase in the acid concentrations led to a decline in the z-value of the microorganisms, being greater in the clear apple juice than in the apple

Mazzotta (2001) recommended a general thermal process of 3 seconds at 71.1 ºC for achieving a 5-log reduction of Escherichia coli O157:H7, Salmonella and Listeria monocytogenes in apple juices adjusted to a pH of 3.9. They reported that pH ranges from 3.6 to 4.0 in apple juice had no significant impact in the heat resistance of E. coli O157:H7. However, the acid tolerance of some microorganisms including E. coli and Salmonella let to the use of chemical preservatives such as benzoic acid in pome fruit juices to help processors to increase substantially the safety of the pasteurized products (Albashan 2009; Koodie & Dhople 2001). According to the Food and Drug Administration (FDA) recommendations, the pasteurization process must ensure a 5-log reduction of the three stated vegetative bacterial pathogens (E. coli O157:H7, Salmonella and L. monocytogenes) at pH values of 3.9. However, thermal destruction of the protozoan parasite Cryptosporidium parvum oocysts causing illness outbreaks associated with the consumption of apple juice must be taken into consideration. Published studies suggest that C. parvum might be more resistant to heat processing than the indicated three vegetative bacterial pathogens (Deng & Cliver 2001). Therefore, FDA suggests that a treatment of 71.7 ºC for 15 seconds for apple juice at pH values of 4.0 or less to achieve the 5-log reduction for the