Effect of leaving milk trucks empty and idle for 6 h between raw milk loads

Abstract

The US Pasteurized Milk Ordinance (PMO) allows milk tanker trucks to be used repeatedly for 24 h before mandatory clean-in-place cleaning, but no specifications are given for the length of time a tanker can be empty between loads. We defined a worst-case hauling scenario as a hauling vessel left empty and dirty (idle) for extended periods between loads, especially in warm weather. Initial studies were conducted using 5-gallon milk cans (pilot-scale) as a proof-of-concept and to demonstrate that extended idle time intervals could contribute to compromised raw milk quality. Based on pilot-scale results, a commercial hauling study was conducted through partnership with a Pacific Northwest dairy co-op to verify that extended idle times of 6 h between loads have minimal influence on the microbiological populations and enzyme activity in subsequent loads of milk. Milk cans were used to haul raw milk (load 1), emptied, incubated at 30°C for 3, 6, 10, and 20 h, and refilled with commercially pasteurized whole milk (load 2) to measure cross-contamination. For the commercial-scale study, a single tanker was filled with milk from a farm known to have poorer quality milk (farm A, load 1), emptied, and refilled immediately (0 h) or after a delay (6 h) with milk from a farm known to have superior quality milk (farm B, load 2). In both experiments, milk samples were obtained from each farm's bulk tank and from the milk can or tanker before unloading. Each sample was microbiologically assessed for standard plate count (SPC), lactic acid bacteria (LAB), and coliform counts. Selected isolates were assessed for lipolytic and proteolytic activity using spirit blue agar and skim milk agar, respectively. The pilot-scale experiment effectively demonstrated that extended periods of idle (>3 h) of soiled hauling vessels can significantly affect the microbiological quality of raw milk in subsequent loads; however, extended idle times of 6 h or less would not measurably compromise milk quality in subsequent loads in commercial tankers. Current tanker sanitation practices appear to be sufficient for maintaining raw milk SPC, LAB, and coliform levels, which are important measures of milk quality.

Calidad bacteriológica de la leche cruda bovina almacenada en el centro de acopio Mocha. Tungurahua. Ecuador

“…Ecuador ha venido trabajando, a través de sus entidades estatales de control fitosanitario en la implementación de acciones para mejorar la calidad de la leche cruda, mediante la certificación de buenas prácticas pecuarias en producción de leche, sin embargo, aún prevalecen las condiciones que hacen propicio el crecimiento de bacterias, entre ellas las patógenas, en la leche producida en las diferentes regiones del país (Nogales y Granada, 2012). Dentro de los factores relevantes que afectan también la composición de la microbiota de la leche cruda se encuentran el tipo de forraje (pasto, ensilado y heno) con el cual se alimenta a los animales, las condiciones higiénicas de los animales y las condiciones de almacenamiento de la leche (Kuhn et al, 2018;Lan et al, 2017).…”

Deciphering the Mechanism by Which Carbon Dioxide Extends the Shelf Life of Raw Milk: A Microbiomics- and Metabolomics-Based Approach

“…The diversity of microbial communities in raw milk is usually considered as one of the key factors affecting milk quality, because udder surfaces, milking instruments, containers and environment are potential sources of microorganisms, which leads to microorganisms being inevitable in raw milk [ 4 ]. Given its nutrient-rich composition, raw milk provides an optimal environment and a nutrient matrix that facilitate rapid microbial reproduction [ 5 ]. Consequently, this can result in undesirable outcomes, such as off-flavors, sourness, discoloration, and a loss of the characteristic freshness associated with milk [ 1 ].…”

“…The heat-resistant proteases and lipases produced during the heat treatment process before processing cannot be completely inactivated, leading to a decrease in the yield and quality of dairy products, such as high-temperature sterilized milk, cheese, yogurt, and ice cream [ 8 ]. To ensure the provision of high-quality and safe dairy products while prioritizing consumer health and satisfaction, it is imperative to implement effective control measures aimed at mitigating or eliminating microbial hazards inherent in raw milk [ 2 , 5 ].…”

Deciphering the Mechanism by Which Carbon Dioxide Extends the Shelf Life of Raw Milk: A Microbiomics- and Metabolomics-Based Approach

“…Microorganisms play a pivotal role in influencing the quality of raw milk. Given its nutrient-rich composition, raw milk provides an optimal environment and nutrient matrix that facilitate rapid microbial reproduction [4]. Consequently, this can result in undesirable outcomes, such as off-flavors, sourness, discoloration, and a loss of the characteristic freshness associated with milk [1].…”

“…This process may lead to a reduction in the nutrient content of raw milk, thereby impacting the nutritional value of the final dairy product [5]. To ensure the provision of high-quality and safe dairy products while prioritizing consumer health and satisfaction, it is imperative to implement effective control measures aimed at mitigating or eliminating microbial hazards inherent in raw milk [2,4].…”