Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2008
Publication Date: 3/20/2009
Citation: Sampedro, F., Geveke, D.J., Fan, X., Rodrigo, D., Zhang, H.Q. 2009. Shelf-Life Study of an Orange Juice-Milk Based Beverage after PEF and Thermal Processing. Journal of Food Science. 74(2):S107-S112.
Interpretive Summary: New minimally processed foods such as beverages composed of orange juice and milk with fortified vitamins, minerals and fiber have appeared on the market due to consumer’s growing demand for natural and healthy products. Pectin methyl esterase (PME) is an important enzyme in orange juice-based products because it causes cloud loss and jellification. Currently, the industry is relying on thermal pasteurization to inactivate PME activity and to extend shelf-life. However, thermal treatment can alter aroma, color and other attributes of the product. Therefore, this study was conducted to investigate quality and shelf-life of an orange juice-milk based beverage treated with traditional thermal process and Pulsed Electric Field (PEF), a non-thermal processing technology. Conditions that inactivated 90% PME activity were used for both PEF and thermal processes. Results showed that both processes reduced microbial population and extended shelf-life of the beverage. PEF processed sample, however, had a slightly longer shelf-life with superior quality than the thermal processed sample. The information will facilitate commercial application of PEF which provides consumers with high quality juice products.
Technical Abstract: The effect of thermal and pulsed electric field (PEF) processing on the shelf-life of an orange juice-milk beverage (OJMB) was studied. The intensities of the treatments were selected to produce similar inactivation of pectin methyl esterase (PME), an enzyme responsible for the jellification and loss of fresh juice cloudiness. Physical properties (pH, Brix and color), microbial population, PME activity and volatile compounds of the product were analyzed during 4-week storage at 8-10 C. The pH was not affected by any treatment but decreased during the storage in the untreated sample. The Brix values were decreased by the two treatments. The thermal and PEF treatments initially inactivated PME activity by 90%. During storage the PME activity remained constant in the two treated samples and decreased slightly in the untreated sample. The reductions in bacterial as well as yeast and mold counts were similar after the two treatments (4.5 and 4.1 log CFU/mL for thermal vs 4.5 and 5.0 log CFU/mL for PEF). Based on the initial bacterial counts of the control, it was estimated that the shelf-lives of the OJMB treated with thermal and PEF processing stored at 8-10 C were 2 and 2.5 weeks, respectively. Differences were observed in the color parameters of the OJMB between the two treatments in comparison with the control, with a higher difference observed in the thermally processed samples. The relative concentration of volatile compounds was higher in OJMB processed by PEF treatment than that in the thermally processed sample. During storage the loss of volatile compounds was lower in the PEF sample while thermal and control samples had a similar rate of loss. For an OJMB, treatment with PEF achieved the same degree of microbial and enzyme inactivation as the thermal treatment, but better preserved color and flavor compounds.