Batches Of Milk Research Articles

Target Fortification of Breast Milk: Predicting the Final Osmolality of the Feeds.

For preterm infants, it is common practice to add human milk fortifiers to native breast milk to enhance protein and calorie supply because the growth rates and nutritional requirements of preterm infants are considerably higher than those of term infants. However, macronutrient intake may still be inadequate because the composition of native breast milk has individual inter- and intra-sample variation. Target fortification (TFO) of breast milk is a new nutritional regime aiming to reduce such variations by individually measuring and adding deficient macronutrients. Added TFO components contribute to the final osmolality of milk feeds. It is important to predict the final osmolality of TFO breast milk to ensure current osmolality recommendations are followed to minimize feeding intolerance and necrotizing enterocolitis. This study aims to develop and validate equations to predict the osmolality of TFO milk batches. To establish prediction models, the osmolalities of either native or supplemented breast milk with known amounts of fat, protein, and carbohydrates were analyzed. To validate prediction models, the osmolalities of each macronutrient and combinations of macronutrients were measured in an independent sample set. Additionally, osmolality was measured in TFO milk samples obtained from a previous clinical study and compared with predicted osmolality using the prediction equations. Following the addition of 1 g of carbohydrates (glucose polymer), 1 g of hydrolyzed protein, or 1 g of whey protein per 100 mL breast milk, the average increase in osmolality was 20, 38, and 4 mOsm/kg respectively. Adding fat decreased osmolality only marginally due to dilution effect. Measured and predicted osmolality of combinations of macronutrients as well as single macronutrient (R2 = 0.93) were highly correlated. Using clinical data (n = 696), the average difference between the measured and predicted osmolality was 3 ± 11 mOsm/kg and was not statistically significant. In conclusion, the prediction model can be utilized to estimate osmolality values after fortification.

Preservatives and neutralizing substances in milk: analytical sensitivity of official specific and nonspecific tests, microbial inhibition effect, and residue persistence in milk

<p>Milk fraud has been a recurring problem in Brazil; thus, it is important to know the effect of most frequently used preservatives and neutralizing substances as well as the detection capability of official tests. The objective of this study was to evaluate the analytical sensitivity of legislation-described tests and nonspecific microbial inhibition tests, and to investigate the effect of such substances on microbial growth inhibition and the persistence of detectable residues after 24/48h of refrigeration. Batches of raw milk, free from any contaminant, were divided into aliquots and mixed with different concentrations of formaldehyde, hydrogen peroxide, sodium hypochlorite, chlorine, chlorinated alkaline detergent, or sodium hydroxide. The analytical sensitivity of the official tests was 0.005%, 0.003%, and 0.013% for formaldehyde, hydrogen peroxide, and hypochlorite, respectively. Chlorine and chlorinated alkaline detergent were not detected by regulatory tests. In the tests for neutralizing substances, sodium hydroxide could not be detected when acidity was accurately neutralized. The yogurt culture test gave results similar to those obtained by official tests for the detection of specific substances. Concentrations of 0.05% of formaldehyde, 0.003% of hydrogen peroxide and 0.013% of sodium hypochlorite significantly reduced (P<0.05) the microbial counts in milk after 24 and 48h refrigeration. Formaldehyde and sodium hypochlorite remained detectable in milk after 48 and 24h of refrigeration, respectively; while hydrogen peroxide could not be detected after 24h. Official tests for the detection of milk fraud by the addition of preservatives and neutralizing substances present limitations and may be ineffective in detecting milk adulteration</p>

Effect of processing of cow milk by high pressures under conditions up to 900 MPa on the composition of neutral, polar lipids and fatty acids

Thermal processing of milk promotes oxidation reactions and changes in organoleptic characteristics. Application of High Pressure Processing (HPP) is a promising alternative but little is known about the impact on milk compounds, mainly lipids. This research aims to study the possible alteration of the composition of milk lipids and fatty acids as result of HPP using 250–900 MPa. Thus, two cow milk batches were assayed and the composition in tri-., di-., monoacylglycerols, cholesterol, cholesterol esters, free fatty acids, phospholipids and fatty acids analysed. It was found differences (p < 0.05) among batches in the distribution of triacylglycerols (CN34, CN50 and CN54) and also in the concentration of diacylglycerols, monoacylglycerols, cholesterol, phosphatidylethanolamine and phosphatidylinositol and unsaturated fatty acids (C18:1 10t, C18:1 9c, C18:1 11c, C18:1 16t+14c, C18:2 9c,12c, C18:2 9c,11t and C20:1 9c). Data from the current study showed that processing by HPP up to 900 MPa did not produce significant changes to the lipid classes or fatty acid composition of milk fat.

Stability of fatty acid composition after thermal, high pressure, and microwave processing of cow milk as affected by polyunsaturated fatty acid concentration

Interest has been increasing to enhance the contents of healthy polyunsaturated fatty acid (PUFA) in milk. However, trans fatty acids and conjugated linoleic acid (CLA) can be altered after thermal processing and high pressures disrupt the milk fat globule membrane, exposing the lipid core and helping its oxidation. The objective of the present research was to study whether processing can alter the fatty acid composition of milk and if these changes are affected by PUFA concentration as previous studies suggest. Two cow milk batches (500L each), one naturally enriched in PUFA, were processed to obtain pasteurized; high temperature, short time; UHT; high pressure; and microwave pasteurized samples. The detailed fatty acid composition was analyzed with special attention to trans fatty acids and CLA isomers. Results showed that after high temperature, short time processing, total CLA content increased in both milk batches, whereas sterilization resulted in a sigmatropic rearrangement of C18:2 cis-9,trans-11 to C18:2 trans-9,trans-11. The extent of these effects was greater in milks naturally enriched in PUFA.

Effect of microbiological testing on subsequent mid-infrared milk component analysis of the same milk sample

Our objectives were to determine if mixing and sampling of a raw milk sample at 4°C for determination of total bacteria count (TBC) and if incubation at 14°C for 18h and sampling for a preliminary incubation (PI) count influenced the accuracy of subsequent fat, protein, or lactose measurement by mid-infrared (IR) analysis of milk from the same sample container due to either nonrepresentative sampling or the presence of microbial metabolites produced by microbial growth in the milk from the incubation. Milks of 4 fat levels (2.2, 3, 4, and 5%) reflected the range of fat levels encountered in producer milks. If the portion of milk removed from a cold sample was not representative, then the effect on a milk component test would likely be larger as fat content increases. Within the milks at each fat level, 3 treatments were used: (1) 20 vials of the same milk sampled for testing TBC using a BactoScan FC and then used for a milk component test; (2) 20 vials for testing TBC plus PI count followed by component test; and (3) 20 vials to run for IR component test without a prior micro sampling and testing. This was repeated in 3 different weeks using a different batch of milk each week. No large effect on the accuracy of component milk testing [IR fat B (carbon hydrogen stretch) and fat A (carbonyl stretch)] due to the cold milk sample handling and mixing procedures used for TBC was detected, confirming the fact that the physical removal of milk from the vial by the BactoScan FC (Foss Electric, Hillerød, Denmark) was a representative portion of the milk. However, the representativeness of any other sampling procedure (manual or automated) of a cold milk sample before running milk component testing on the same container of milk should be demonstrated and verified periodically as a matter of routine laboratory quality assurance. Running TBC with a BactoScan FC first and then IR milk analysis after had a minimal effect on milk component tests by IR when milk bacteria counts were within pasteurized milk ordinance limits of <100,000 cfu/mL. Running raw milk PI counts (18h of incubation at 13–14°C) with the BactoScan FC before milk component testing by IR milk analysis had an effect on component tests. The effect was largest on fat test results and would decrease the accuracy of milk payment testing on individual producer milks. The effect was most likely due to the absorption of light by bacterial metabolites resulting from microbial growth or other chemical degradation processes occurring in the milk during the PI count incubation, not by the sampling procedure of the BactoScan. The direction of the effect on component test results will vary depending on the bacteria count and the type of bacteria that grew in the milk, and this could be different in every individual producer milk sample.

Process standardization for the manufacture of Thabdi Peda.

Traditional dairy products in India are manufactured using age old methods. Such methods varies from place to place. For industrial production of such products a standardized process is needed. Present study was designed to arrive at a method of manufacture for Thabdi Peda, a very popular sweet in Saurashtra region of Gujarat. Range of process parameters like fat percent of milk (4 to 8%), rate of sugar addition (6 to 10%) and duration of final heat desiccation (20 to 60min) were studied and optimum values determined using Response Surface Methodology (RSM) with central composite rotatable design (CCRD). The samples obtained from trials were analyzed for sensory, physicochemical, compositional and textural attributes. The optimized process developed with 10kg batch of milk having 6% fat, 8.33% rate of sugar addition and 34min duration of heating produced most acceptable product. Standardized Thabdi Peda was found to contain on an average 16.80% fat, 17.48% moisture, 11.25% protein, 20.95% lactose, 29.99% sucrose, 3.53% ash and it gave 28.75% yield. The pH, water activity and HMF (μ Mole/100g) content were 6.42, 0.807 and 121.91 respectively. Standard plate count, Yeast and Mold counts were observed to be 3.68log cfu/g, and 2.51log cfu/g respectively. No coliforms were observed in Thabdi Peda.

Effect of season and herd on rennet coagulation time and other parameters of milk technological quality in Holstein dairy cows

In five herds of purebred Holstein dairy cows, altogether 220 bulk milk samples were collected with the following average parameters: rennet coagulation time (RCT) 265.2 sec., titratable acidity 6.40 °SH, active acidity 6.72 pH, specific density 1.0281 kg.l−1, fat content 3.81 g.100g−1, protein content 3.28 g.100g−1, lactose content 4.72 g.100g−1, and content of solids non-fat content 8.89 g.100g−1; average values of milk batch volume per herd and diurnal air temperature were 6,072 kg and 8.02 °C, respectively. It was found out that the variable “season“ (spring, summer, autumn or winter) significantly influenced nearly all parameters under study (the only exceptions were values of titratable acidity and milk batch volume). As compared with all other seasons, the significantly shortest RCT was recorded in summer. Further it was also found out that the variable “herd” influenced all parameters with the exception of average diurnal air temperature. Regardless to differences existing among individual herds, the shortest average RCT was recorded always in summer.

Lipid oxidation volatiles absent in milk after selected ultrasound processing

Ultrasonic processing can suit a number of potential applications in the dairy industry. However, the impact of ultrasound treatment on milk stability during storage has not been fully explored under wider ranges of frequencies, specific energies and temperature applications. The effect of ultrasonication on lipid oxidation was investigated in various types of milk. Four batches of raw milk (up to 2L) were sonicated at various frequencies (20, 400, 1000, 1600 and 2000kHz), using different temperatures (4, 20, 45 and 63°C), sonication times and ultrasound energy inputs up to 409kJ/kg. Pasteurized skim milk was also sonicated at low and high frequency for comparison. In selected experiments, non-sonicated and sonicated samples were stored at 4°C and were drawn periodically up to 14days for SPME–GCMS analysis. The cavitational yield, characterized in all systems in water, was highest between 400kHz and 1000kHz. Volatile compounds from milk lipid oxidation were detected and exceeded their odor threshold values at 400kHz and 1000kHz at specific energies greater than 271kJ/kg in raw milk. However, no oxidative volatile compounds were detected below 230kJ/kg in batch systems at the tested frequencies under refrigerated conditions. Skim milk showed a lower energy threshold for oxidative volatile formation. The same oxidative volatiles were detected after various passes of milk through a 0.3L flow cell enclosing a 20kHz horn and operating above 90kJ/kg. This study showed that lipid oxidation in milk can be controlled by decreasing the sonication time and the temperature in the system depending on the fat content in the sample among other factors.

Bioavailability and Allergoprotective Capacity of Milk-Associated Conjugated Linoleic Acid in a Murine Model of Allergic Airway Inflammation

Background: Cross-sectional epidemiological studies have demonstrated that farm milk from traditional farm settings possesses allergoprotective properties. Up to now, it has not been clarified which milk ingredient is responsible for protection against allergic diseases. As farm milk is rich in conjugated linoleic acids (CLA), it is hypothesized that this n-3 polyunsaturated fatty acid family contributes to the allergoprotective capacity of farm milk. We aim to prove this hypothesis in a murine model of allergic airway inflammation. Methods: To prove the bioavailability and allergoprotective capacity of milk-associated CLA in a standardized protocol, milk batches that differed significantly in terms of their CLA content were spray dried and incorporated into a basic diet by substituting the regular sunflower fat fraction. Initially, the milk CLA uptake from the diet was monitored via measurement of the CLA content in plasma and erythrocyte membranes obtained from supplemented mice. To determine whether a milk CLA-enriched diet possesses allergoprotective properties, female Balb/c mice were fed the milk CLA-enriched diet ahead of sensitization and a challenge with ovalbumin (OVA) and the parameters of airway inflammation and eisosanoid pattern were measured. Results: In animals, supplementation with a diet rich in milk CLA resulted in elevated CLA levels in plasma and erythrocyte membranes, indicating bioavailability of milk fatty acids. Though membrane-associated phospholipid patterns were affected by supplementation with milk CLA, this application neither reduced the hallmarks of allergic airway inflammation in sensitized and OVA-challenged mice nor modified the eiconsanoid pattern in the bronchoalveolar lavage fluid of these animals. Conclusion: Milk-associated CLA was not capable of preventing murine allergic airway inflammation in an animal model of OVA-induced allergic airway inflammation.

The effect of immunoglobulins and somatic cells on the gravity separation of fat, bacteria, and spores in pasteurized whole milk

Our objective was to determine the role that immunoglobulins and somatic cells (SC) play in the gravity separation of milk. The experiment comprised 9 treatments: (1) low-temperature pasteurized (LTP; 72°C for 17.31s) whole milk; (2) LTP (72°C for 17.31s) whole milk with added bacteria and spores; (3) recombined LTP (72°C for 17.31s) whole milk with added bacteria and spores; (4) high-temperature pasteurized (HTP; 76°C for 7min) whole milk with added bacteria and spores; (5) HTP (76°C for 7min) whole milk with added bacteria and spores and added colostrum; (6) HTP (76°C for 7min) centrifugally separated, gravity-separated (CS GS) skim milk with HTP (76°C for 7min) low-SC cream with added bacteria and spores; (7) HTP (76°C for 7min) CS GS skim milk with HTP (76°C for 7min) high-SC cream with added bacteria and spores; (8) HTP (76°C for 7min) CS GS skim milk with HTP (76°C for 7min) low-SC cream with added bacteria and spores and added colostrum; and (9) HTP (76°C for 7min) CS GS skim milk with HTP (76°C for 7min) high-SC cream with added bacteria and spores and added colostrum. The milks in the 9 treatments were gravity separated at 4°C for 23h in glass columns. Five fractions were collected by weight from each of the column treatments, starting from the bottom of the glass column: 0 to 5%, 5 to 90%, 90 to 96%, 96 to 98%, and 98 to 100%. The SC, fat, bacteria, and spores were measured in each of the fractions. The experiment was replicated 3 times in different weeks using a different batch of milk and different colostrum. Portions of the same batch of the frozen bacteria and spore solutions were used for all 3 replicates. The presence of both SC and immunoglobulins were necessary for normal gravity separation (i.e., rising to the top) of fat, bacteria, and spores in whole milk. The presence of immunoglobulins alone without SC was not sufficient to cause bacteria, fat, and spores to rise to the top. The interaction between SC and immunoglobulins was necessary to cause aggregates of fat, SC, bacteria, and spores to rise during gravity separation. The SC may provide the buoyancy required for the aggregates to rise to the top due to gas within the SC. More research is needed to understand the mechanism of the gravity-separation process.

Quantitative traceability modelling and optimisation for dairy manufacturing process

Generally several batches of raw milk are mixed to produce several kinds and batches of dairy products which makes traceability difficult. To clarify the many-to-many relationships between batches of raw milk and products, a quantitative traceability model is established. The traceability model treats the interval between two cleans in place (CIPs) of the storage tank as a research cycle and uses iterative equations to describe the quantitative relationship between batches of raw milk and products. With a goal to narrow the scope of a product recall, the traceability model transforms into an optimisation model, which can optimise the schedule of production and the time that raw milk is pumped into storage tanks. The simulation verifies that the traceability model can clearly show the quantitative relationships between raw milk and products, and the optimisation model can significantly reduce the complexity of traceability and narrow the scope of product recalls.

Quantitative Detection of Shiga Toxin-Producing and Enteropathogenic Escherichia coli Serotypes O157 and O26 in Bulk Raw Milk

The presence of pathogens must be adequately monitored in raw milk and dairy products to assess their safety. With this aim, sampling plans and analytical methods should be evaluated for their appropriateness. Five incremental samples were collected from 40 milk tankers and overall 200 individual samples were analysed to assess the number and distribution of Escherichia coli O157 and O26. Enriched samples were screened by PCR for the presence of the serogroup-specific genes rfbEO157 and wzxO26, and the positive cultures were analysed by reverse transcriptase-PCR to detect mRNA sequences encoded by these genes, which are indicative of the presence of viable bacteria. In addition, the numbers of E. coli O157 and O26 in milk were estimated by most-probable-number–PCR method. The results of PCR screening targeting the rfbEO157 and wzxO26 genes were positive in 34 samples (representing 15 batches) and complementary mRNA sequences were detected in 27 of these (80 %). Isolation from the enriched cultures resulted in detection of E. coli O157 in 100 % of the enriched samples positive for the O157 RNA marker, whereas E. coli O26 was isolated from only 37.5 % of the enriched cultures positive for O26 RNA marker. E. coli strains that produce Shiga toxins O26:H11 was isolated from one batch (2.5 %), while typical enteropathogenic E. coli O26 and non-pathogenic strains of E. coli O157 were isolated from four other batches. Estimated by most-probable-number (MPN), the number of E. coli O157 or O26 was below 0.3 MPN ml−1 in all the milk samples, except two that had MPN equal to 1.4∙ml−1 (CI95% 0.36–4.2). The distribution of E. coli O157 and O26 within the milk batches was not uniform. Seven (47 %) of the 15 batches with positive results for either the O157 or O26 gene had only one incremental sample positive out of five samples analysed. In the presence of very low concentrations of pathogens, the sampling method used may affect the probability of detection of ‘defective’ batches.

Target Fortification of Breast Milk with Fat, Protein, and Carbohydrates for Preterm Infants

Fortification of breast milk is an accepted practice for feeding very low birth weight infants, however, fixed dosage enhancement does not address variations in native breast milk. This could lead to deficiencies in calories and macronutrients. We therefore established the infrastructure for target fortification in breast milk by measuring and adjusting fat, protein, and carbohydrate content daily. We analyzed nutrient intake, growth, and safety variables. Each 12-hour batch of breast milk was analyzed using near-infrared spectroscopy. Macronutrients were individually added to routine fortification to achieve final contents for fat (4.4 g), protein (3 g), and carbohydrates (8.8 g) (per 100 mL). Fully breast milk fed healthy very low birth weight infants (<32 weeks) were fed the fortified breast milk for at least 3 weeks. Matched pair analysis of 20 infants fed routinely fortified breast milk was performed using birth weight, gestational age, and postnatal age. All 650 pooled breast milk samples required at least 1 macronutrient adjusted. On average, 0.3 ± 0.4 g of fat, 0.7 ± 0.2 g of protein, and 1.2 ± 0.2 g of carbohydrate were added. Biochemistry was normal in the 10 target fortified infants (birth weight: 860 ± 309 g, 26.3 ± 1.6 weeks gestational age); weight gain was 19.9 ± 2.7 g/kg/d; and milk intake was 147 ± 5 mL/kg/d (131 ± 16 kcal/kg/d). Osmolality of fortified breast milk was 436 ± 13 mOsmol/kg. Matched pair analysis of infants indicated a higher milk intake (155 ± 5 mL/kg/d) but similar weight gain (19.7 ± 3.3 g/kg/d). No adverse event was observed. The linear relationship between milk intake and weight gain observed in study babies but not seen in matched controls may be related to the variable composition of breast milk. Daily target fortification can be safely implemented in clinical routine and may improve growth.

The dairy chains in North Africa (Algeria, Morocco and Tunisia): from self sufficiency options to food dependency?

The Maghreb countries (Algeria, Morocco and Tunisia) have experienced since the early 1950s a rapid demographic growth coupled to a significant rhythm of urbanization. This has led to a marked increase in the demand of dairy products. In order to secure the supply, specific policies have been implemented. They mainly consisted in the establishment of a dairy industry, based on the processing of either raw milk produced locally (in Morocco and Tunisia) or imported milk powder (in Algeria). These divergent options have had significant consequences on the whole organization of the dairy chains in these countries, from cattle rearing practices, to milk collection and processing. They have also implied differences in milk and its derivatives’ prices and levels of consumption. The paper draws a comparative analysis of milk chains within the three countries: a supply mainly based on imports in Algeria, whereas in Morocco and Tunisia, the demand is satisfied by a chain relying on locally produced cattle milk. The paper also emphasizes on the future challenges that will have to be addressed: a rising volatility of milk and other strategic inputs’ prices (feed, machinery, cattle, etc.) in global markets, an improvement in consumers’ awareness about milk quality, a further pressure on natural resources (mainly soils and water) to get more raw milk, in countries already suffering an acute water stress. The article also establishes recommendations about specific issues related to the development of the dairy chains in the context of North Africa. These are mainly linked to the fragmented offer induced by numerous smallholder farms, which implies obvious difficulties to assess the hygienic and the chemical quality of milk batches delivered daily. Moreover, this fragmented offer also means that specific support programs will have to be designed, as the vast majority of farms are not dairy specialized, expecting both milk and calf crop from their herds.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-162) contains supplementary material, which is available to authorized users.

Production of an 18% protein liquid micellar casein concentrate with a long refrigerated shelf life

Our objective was to develop a process to produce a high-concentration liquid micellar casein concentrate (18% protein, MCC18) with a long refrigerated shelf life. The MCC18 is a novel milk protein ingredient produced by fractionating skim milk using microfiltration (MF). To achieve a long refrigerated shelf life, the processing of MCC18 was designed to maximize the removal of low-molecular weight compounds [e.g., lactose and nonprotein nitrogen (NPN)] that can be easily metabolized by microbes, while minimizing the microbial count in the final product. The production of MCC18 was done over a period of 5 d. The experiment was replicated 3 times in different weeks with a different batch of raw milk. Raw whole milk was pasteurized and separated to produce skim milk. Skim milk was ultrafiltered (UF) to remove more than half of the lactose and NPN. The UF milk retentate was diluted with water and then MF in 3 stages to remove approximately 95% of the serum protein and further remove lactose and NPN. The retentate from the last stage of MF was UF to concentrate the protein to 18% and batch pasteurized. The MCC18 was collected immediately after processing in sterile plastic vials and stored at 4°C. The average MCC18 contained 21.78% total solids, 18.27% true protein, 0.31% NPN, and 0.13% lactose. The MCC18 at the day of processing contained a mean aerobic bacterial count of 2.1 log cfu/mL and mean aerobic spore count of 2.3logcfu/mL. The MCC18 formed a solid gel at temperatures <22°C, but the MCC18 reverted back to a liquid when warmed from 4°C temperature to >22°C. This provides a unique opportunity in ingredient handling and packaging and eliminates the challenges encountered in reconstitution of dried milk protein ingredients. The MCC18 produced in this study maintained a bacteria count <20,000 cfu/mL for 16wk when stored at a refrigeration temperature of 4°C. Further study is needed to determine if changes occur in the organoleptic and functional properties of MCC18. We envision that the conversion of skim milk to MCC and its coproducts (serum protein concentrate and lactose concentrate) could be used as an alternative to the production of nonfat dry milk to balance milk production seasonality, specifically the components of skim milk portion.

Influence of casein on flux and passage of serum proteins during microfiltration using polymeric spiral-wound membranes at 50°C

Raw milk (approximately 1,800kg) was separated at 4°C, pasteurized (at 72°C for 16s), and split into 2 batches. One batch (620kg) was microfiltered (MF) using pilot-scale ceramic uniform transmembrane pressure Membralox membranes (model EP1940GL0.1μA, 0.1-μm alumina; Pall Corp., East Hills, NY) to produce retentate and permeate. The permeate from the MF uniform transmembrane pressure was casein-free skim milk (CFSM). The CFSM was MF using polymeric spiral-wound (SW) membranes (model FG7838-OS0x-S, 0.3 μm; Parker-Hannifin Corp., Process Advanced Filtration Division, Tell City, IN) at a concentration factor of 3× and temperature of 50°C. Following the processing of CFSM, the second batch of skim milk (1,105kg) was processed using the same polymeric membranes to determine how casein content in the feed material for MF with polymeric membranes affects the performance of the system. There was little resistance to passage of milk serum proteins (SP) through a 0.3-μm polyvinylidene fluoride (PVDF) SW membrane at 50°C and no detectable increase in hydraulic resistance of the membrane when processing CFSM. Therefore, milk SP contributed little, if any, to fouling of the PVDF membrane. In contrast, when processing skim milk containing a normal concentration of casein, the flux was much lower than when processing CFSM (17.2 vs. 80.2kg/m2 per hour, respectively) and the removal of SP from skim milk with a single-pass 3× bleed-and-feed MF system was also much lower than from CFSM (35.2 vs. 59.5% removal, respectively). Thus, when processing skim milk with a PVDF SW membrane, casein was the major protein foulant that increased hydraulic resistance and reduced passage of SP through the membrane.

On-Farm Pasteurized Milk Fed To Dairy Calves Association Of Bacteria Counts Following Pasteurization With Season, Temperature And Time Until Feeding

On-farm pasteurization of waste milk fed to calves has become increasingly common over the last 15 years. This study investigated bacteria counts in milk before pasteurization and for 24 h following pasteurization at varying storage temperatures associated with seasons. Standard plate counts on Aerobic Count Plate PetrifilmTM to enumerate bacterial colony concentration were measured on raw and post-pasteurized milk after pasteurization at 63°C (145°F) for 30 min using commercial pasteurizers on 3 different commercial dairy farms. Each farm was sampled in each of 4 seasons of the year. All 12 batches of milk were divided into 2 aliquots. One aliquot was incubated at controlled temperature to mimic the season (refrigerated, room temperature, or incubated at 37 °C) and the other was incubated at ambient outdoor temperatures. The SPC was determined at pre-pasteurization, 0 (immediately post-pasteurization), 1, 2, 3, 4, 5, 6, 7, 8, 10, 12 and 24 h post-pasteurization. The final general linear model testing for factors associated with LogSPC was highly explanatory (R2=0.71), and significant (P<0.0001). This final model for LogSPC included time since pasteurization, season, farm, the interaction of time and season, and the interaction of season and farm. The model showed that passage of time was associated with increased LogSPC, especially during summer. In a northern temperate climate under the conditions observed during this study, milk - could safely be fed-if defined as SPC<20,000 cfu/ml-for at least 8 h post-pasteurization during fall and spring, and for 24 h during winter, but only for 3 h if milk was stored outside during the summer. These results suggest that for milk kept outdoors during summer, any milk remaining after first feeding following pasteurization should not be fed to calves at subsequent feedings, but instead should be re-pasteurized or discarded.

Microbial biodiversity, quality and shelf life of microfiltered and pasteurized extended shelf life (ESL) milk from Germany, Austria and Switzerland

Information on factors limiting the shelf life of extended shelf life (ESL) milk produced by microfiltration and subsequent pasteurization is very limited. In this study, three different batches of ESL milk were analyzed at different stages of the production process and during storage at 4 °C, 8 °C and 10 °C in order to evaluate the changes in bacterial cell counts, microbial diversity and enzymatic quality. Additionally, detailed biodiversity analyses of 250 retail ESL milk packages produced by five manufacturers in Germany, Austria and Switzerland were performed at the end of shelf life. It was observed that microfiltration decreased the microbial loads by 5-6 log₁₀ units to lower than 1 CFU/mL. However, bacterial counts at the end of shelf life were extremely variable and ranged between <1 and 8 log₁₀ CFU/mL. 8% of all samples showed spoilage indicated by cell counts higher than 6 log₁₀ CFU/mL. The main spoilage groups of bacteria were Gram-negative post-process recontaminants (Acinetobacter, Chryseobacterium, Psychrobacter, Sphingomonas) and the spore formers Paenibacillus and Bacillus cereus, while other spore formers and Microbacterium spp. did not reach spoilage levels. Paenibacillus spp. and B. cereus apparently influenced enzymatic spoilage, as indicated by increased free fatty acid production, pH 4.6 soluble peptide fractions and off-flavors. In some cases, enzymatic spoilage was observed although microbial counts were well below 6 log₁₀ CFU/mL. Thirteen B. cereus isolates were characterized for their toxin profiles and psychrotolerance. Hbl, nhe, and cytK toxin genes were detected in ten, thirteen, and four isolates, respectively, whereas the ces gene was always absent. Interestingly, only three of the thirteen isolates could be allocated to psychrotolerant genotypes, as indicated by the major cold shock cspA gene signature. Generally, large discrepancies in microbial loads and biodiversity were observed at the end of shelf life, even among packages of the same production batch. We suggest that such unexpected differences may be due to very low cell counts after ESL treatment, causing stochastic variations of initial species distributions in individual packages. This would result in the development of significantly different bacterial populations during cold storage, including the occasional development of high numbers of pathogenic species such as B. cereus or Acinetobacter.

The microbial content of unexpired pasteurized milk from selected supermarkets in a developing country

Objective To determine the presence and levels of microbes in unexpired pasteurized milk from randomly selected supermarkets in Kingston, Jamaica. Methods The quantitative study used a stratified random sampling technique in the selection of the 20 representative milk samples from six (6) supermarkets. Microbiological tests such as methylene blue reduction, standard plate count (SPC), coliform plate count (CPC), purity plate culture, gram staining and biochemical tests were performed to examine the microbes in purchased unexpired pasteurized milk. Results One sample (BCr016) had a pH of 4.0, a rancid odour and curdled appearance. It decolourized within one hour during the methylene blue reduction test and was classified as class 4 milk. Seven of the samples were sterile with no microbe growth on the plate count agar and violet red bile salt agar (VRBA). The milk samples that appeared to be safe for consumption were all 10, 11, 12 and 13 days before expiration. The VRBA sample BCr016, had a colony count of 13 400 CFU/mL. There was the presence of Escherichia coli in sample LCr021 which had a standard plate count of 1 580 SPC/mL and a coliform count of 500 CFU/mL. Enterobacter sp. was present in colonies from BCr016 and all the other milk samples. Conclusions Unacceptable levels of Enterobacter spp. and Escherichia coli were found in most of the samples. Effective measures to ensure safe milk for human consumption such as the phosphatase test and methylene blue reduction test should be routinely performed on each batch of milk processed by dairy plants.

Determination of melamine in different milk batches using a novel chemosensor based on the luminescence quenching of Ru(II) carbonyl complex

A novel, simple, sensitive and precise spectrofluorimetric method was developed for measuring the melamine concentration in different milk batch samples. The method was based upon measuring the quenching of the luminescence intensity of the produced yellow colored ruthenium (II) carbonyl complex of the general formula [Ru(CO) 2(L)] (where L = anion of tetradentate Schiff base). The Ru (II) complex exhibited characteristic luminescence band in the visible region. The remarkable quenching of the luminescence intensity of [Ru(CO) 2(L)] complex by various concentrations of melamine was successfully used as a chemosensor for the assessment of melamine in different milk samples at λ ex = 400 nm and pH 7.4 in DMSO with a linear dynamic range 1.0 × 10 −6 to 3.0 × 10 −9 mol L −1 and lower detection limit (LOD) and quantification detection limit (QOD) of 3.3 × 10 −10 and 1.0 × 10 −9 mol L −1, respectively.