2010, Volume 2, Number 1

Microbiological Quality of Pasteurized Milk in Hawai`i

HONGFEI HE, YONG LI*, ALFRED L. CASTRO, JIN DONG and C. N. LEE*

Abstract: coComplaints of spoilage of pasteurized milk purchased from Honolulu groceries highlighted the need to address the emerging milk quality issues for the consumer’s consumption. The objective of this study was to evaluate the microbiological quality of pasteurized milk available in Hawaii's market. Bacterial counts of different types of milk samples (imported-M, locally produced-L and imported organic-O) were compared during refrigerated storage. Imported bulk milk from mainland are re-pasteurized in Hawaii and packaged under different brands. Hawaii locally produced milk are marketed with the "Island Fresh" label. The expiration or sell by date is based on the pasteurization. Imported organic milk from the mainland were prepackaged and shipped by air freight. At 5d before the expiration date, 70% of the mainland samples and 62% of the local samples had aerobic bacteria count exceeding the regulatory limit of 20,000 cfu/ml for grade ‘A’ pasteurized milk set by the United States Food and Drug Administration (FDA). Local raw milk samples from the farms supplying the processor were examined and results indicated good microbiological quality. High levels of psychrotrophic bacteria were identified as a major contributor to the pasteurized milk spoilage before the expiration date. The implications of this study were further discussed.
Keywords: pasteurized milk, raw milk, re-pasteurization, microbiological quality, shelf-life, spoilage bacteria, psychrotrophic bacteria, post-pasteurization contamination, degradative enzymes, Pasteurized Milk Ordinance.

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