Title of thesis: Nutritional and microbiological quality assessment of milk powder of various brands available in the retail markets of Bangladesh. Because of its concentrated source of many important components, powdered milk has advantages (Hall and Hendrick, 1966). 3 Due to the lack of studies on the quality of milk powder in Bangladesh, customers have little knowledge of higher quality options (Kajal et al., 2012).
Considering the aforementioned information, this study was conducted for the chemical and microbiological analysis of different brands of milk powder in Bangladesh to meet the following objectives-. To evaluate the nutritional and microbiological properties of different brands of milk powder available in Bangladesh.
Definition of milk
History
Uses of dried milk
Processing of powdered milk
If the milk particles come into contact with the hot heat transfer surface during the drying process, the powder may have burnt particles that reduce the quality of the powder (Bylund, 1995). This process involves three steps: first, the concentrate is dispersed into extremely fine droplets; second, it is mixed with a stream of hot air that quickly evaporates the water; and third, the dry milk particles are separated by the drying air. Spray dryers, according to Ozmen and Languish (2003), should be cleaned periodically as dusts tend to accumulate on the walls.
Types of milk powders
7 White Whole Milk No other drying ingredient comes as close to the composition of fresh milk as whole milk powder, which is a soluble powder formed by spray drying fresh whole milk (Thompson, 1996). Typically, it is made by skimming off the water from pasteurized, homogenized whole milk (USDEC, 2006). The following quality criteria apply to whole milk powder: fat content 24.0%, moisture 4.0% and solubility index 1.0.
The Chemical Content of Milk Powder
- Protein content
- Fat content
- Moisture level
- Titratable Acidity
- Ash level
According to Ecklas and Macy (2004), milk's fat content is its most valuable component and plays a significant role in relation to milk's nutritional value. According to BSTI and ADMI (1971), whole milk powder has an average fat content of at least 26%. However, according to Clarence et al. 1951), any change in the proportion of other elements similarly affected the water content.
Issues with milk powder
According to Thomas et al., (2004), the functional qualities of milk proteins have led to the increased acceptance of milk powder as a food ingredient. According to Thomas et al., (2004), lactose crystallization, adhesion and formation issues, and biochemical reactions, especially the Maillard reaction, are the main physicochemical and biochemical damages experienced during storage. According to Thomas et al., (2004), lactose is the most abundant substance in fresh whole milk (4.9%) and lactose is amorphous when spray dried into milk powder.
According to Thomas et al. (2004) the oil droplets are strained within the particles and forced to spread to the surface of the particles. According to Foster et al. (2005) reported caking and setting problems during the preparation and storage of high-fat powders such as cream powder and cheese powder. According to Thomas et al. (2004), the powder collapses when it is not stiff enough to support its own weight.
According to Thomas et al., (2004), the Maillard reaction occurs when reducing sugars and proteins in food interact biochemically. In whole milk powders, lipase activity and the amount of free fatty acids have been investigated by Chen et al., in 2003. According to Chen et al., (2003), proteolysis in milk powder has been assessed by tracking changes in nitrogen levels, such as the increase in non protein nitrogen or drop in casein nitrogen (NPN).
According to Thomas et al., (2004), the proteolytic activity of whole milk powders was not significantly affected by storage.
Microflora in powdered milk
Staphylococcus aureus
Staphylococcus aureus infections in humans are thought to be mostly caused by milk and its derivatives (Zecconi and Piccinini, 1998). In Europe, 5% of staphylococcal epidemics are attributed to milk and other dairy products (Bianchi et al., 2014). Staphylococcus aureus must not be present in 25gm of the product in accordance with Codex stan criteria of.
Screening methods for microorganisms in milk microscopy
Smooth, round pink colonies with scattered growth are produced by Escherichia coli (Anderson et al., 2013). In addition, it is a selective medium for mannitol-fermenting staphylococci, containing the carbohydrate mannitol and the indicator phenol red, a pH indicator for detecting acid produced by mannitol-fermenting staphylococci such as Staphylococcus aureus, which produces yellow colonies with yellow zones, while other staphylococci produce small pink or red colonies with no color change to the medium (Anderson et al., 2013). The indole test is a biochemical procedure used to assess the ability of a bacterial species to convert tryptophan to indole.
The presence of a red or red-purple hue in the surface alcoholic layer of the broth indicates a successful reaction. This is due to the presence of skatole, another potential byproduct of tryptophan breakdown, also known as methyl indole or methylated indole. 15 The triple iron sugar test (TSI) is a microbiological procedure that assesses the ability of a microorganism to form hydrogen sulfide and ferment sugars.
Any of the three sugars in the medium fermented by bacteria produces byproducts. The location of the color shift distinguishes between the acidic byproducts of lactose or sucrose fermentation and the acid formation associated with glucose fermentation. Enterobacteria make up a large part of the bacteria that can ferment carbohydrates in the anaerobic part of the tube.
When fibrinogen is converted to insoluble fibrin in the presence of plasma by coagulase, which is generated by some Gram-positive cocci, including S.
Hygiene aspects of dried milk powder
Blood agar cannot be used for a catalase test because blood contains catalase (Davis and Hoyling, 1973). To avoid contamination of the powder, the drying chamber must be kept in extremely hygienic conditions.
Materials and method
- Test location
- Collection of samples
- Chemical Analysis
- Reconstitution of Powdered milk
- Procedure for the Chemical analysis of powdered milk
- Determination of acidity percentage
- Determination of fat percentage by Gerber Method
- Determination of moisture percentage
- Determination of Crude Protein
- Determination of Ash
- Bacteriological analysis
- Preparation of agar medium
- Enumeration of Total viable bacterial count (TVC)
- Isolation of E coli
- S. aureus isolation
- Statistical Analysis
The butyrometers were placed in the test tube rack only after they had been labeled with the powdered milk brand name. According to the labeling, 11 ml of reconstituted milk was introduced into the butyrometers from the designated cup. Automatic distillation from a connected flask carrying NaOH solution provided 40% NaOH solution to the diluted mixture.
The coal was then placed in a muffle furnace and heated for 4 hours at a temperature of about 600°C to remove all the coal. After that, it was withdrawn, cooled and kept in a desiccator while the weight of the ash box was measured. 1 ml from the first tube was transferred to the second, and so on to the last, and 1 ml from the last tube was discarded.
5 ml of pure bacterial culture was inoculated with 2 ml of sterile tryptophan or peptone broth before the test, and the mixture was then incubated for 24-48 hours at 37°C. After incubation, the culture broth was mixed well with 0.5 ml of Kovac's reagent (isoamyl alcohol, para-Dimethyl-amino-benzaldehyde, concentrated hydrochloric acid). A pure colony of the test organism was inoculated into 5 ml of sterile glucose phosphate peptone broth before being subjected to the Methyl Red (MR) test.
Bound coagulase is a protein bound to the cell wall, while free coagulase is an enzyme released extracellularly.
Results
Chemical properties of milk
There was no statistically significant difference in the Brands milk powder acidity values and 5 for Treatment 1.
Microbiological analysis
- Total Viable Bacterial Count (TVC)
- Escherichia coli
- Staphylococcus aureus
Discussion
The ash of different types of milk powder collected from a local market showed statistically insignificant variations (Table 4). Because the increased moisture would create a moist area that is suitable for the growth of mold or some anaerobic bacteria, the percentage of moisture in milk powder should not exceed 5% (Gasmalla et al., 2013). It was found that the moisture content of different types of powdered milk purchased from the neighborhood market did not differ significantly from each other (Table 5).
The BDS 860:2020 report indicates that the typical amount of moisture present in dried whole milk powder is 5.0. According to the ADMI (1971), the amount of moisture contained in whole milk powder falls somewhere between two and five percent. On the contrary, the BSTI estimates that the amount of moisture that can be present in whole milk powder is no more than 4%.
Compared to the acidity of the other five milk powder samples, the mean value obtained from C for treatment 1 was significantly higher, while the mean value obtained from signs was significantly lower for treatments 1 and 2 (Table 6). According to BSTI and ADMI standards, the accuracy of the present study was satisfactory. The acidity of regular milk samples, which we know to be between 0.10 and 0.18 percent, with an average of 0.16 percent (Eckles, 1951), is very close to the percentage acidity of powdered milk samples collected during the experiment.
This higher number of staphylococci in milk samples may be due to ineffective management and improper hygiene practices during breeding, milking, transport, processing and preparation of the samples (Zakary et al., 2011).
Conclusion
Limitations and Recommendations
Code of principles on milk and milk products (7th edition) Standard for whole milk powder, semi-skimmed milk powder and skimmed milk powder. In: Fundamentals of Dairy chemistry, 2nd Ed., Webb, H.B., Johanson, H. eds.), The AVI Publishing co., Inc., Westport, Connecticut, USA. Isolation of Escherichia Coli from indigenous sweet dairy products of public health relevance sold in sweetmeat shops in Jalandhar, India.
An experimental investigation into the wall deposition of milk powder in a pilot-scale spray dryer. Survival of thermophilic spore forming bacteria in a 90+ year old milk powder from Ernest Shackelton's Cape Royds Hut in Antarctica. Phenotypic and genotypic characteristics of Staphylococcus aureus isolates from raw bulk tank milk samples from goats and sheep.
Isolation of Escherichia Coli from raw milk and milk products of public health concern sold under market conditions in Tandojam, Pakistan. Isolation of Escherichia coli from raw milk and milk products of public health concern sold under commercial conditions at Tandojam. Storage stability of whole milk powder: effects of process and storage conditions on product properties.
Detection of Staphylococcus aureus in bovine milk and its product by real-time PCR assay.
