Investigation of the effect of b-galactosidase enzyme on the storage capacity of low-lactose milk

The article discusses the effect of the b-galactosidase enzyme on the storage capacity of milk with hydrolyzed lactose. For this purpose, parallel studies of a sample of sterilized milk and low-lactose milk, produced on its basis, were carried out. The peptide profile was used as a criterion for assessing the storage capacity of milk that underwent enzymatic decomposition of lactose. Assessment of the state of the peptide profile during storage was recorded at three control points — 30, 60 and 90 days. Studies have shown that at the second checkpoint, peptides were identified that characterize the proteolytic activity in the product. The third checkpoint study revealed the presence of low molecular weight peptides responsible for the bitter taste in milk. Parallel studies of sterilized milk without the addition of the enzyme did not reveal any changes in the peptide profile. The studies carried out indicate that the b-galactosidase enzyme has a residual proteolytic activity, which negatively affects the storage capacity of low-lactose milk and, as a consequence, the products, produced on its basis.

Formula milk increases lactoferrin levels in 7–9 years old children

Background: Lactoferrin is known to have a bacteriostatic or bactericidal effect by binding ions in saliva to interfere with the survival of bacteria that need such ions, such as Streptococcus mutants. Lactoferrin is a whey protein and can be found in formula milk. Purpose: This study aimed to analyse lactoferrin levels before and after consuming formula milk and sterilized milk. Methods: This study was conducted on 22 students aged 7–9 years at Public Elementary School (SD Negeri) 060817 using purposive sampling, with 11 students consuming formula milk and 11 students consuming sterilized milk. Saliva was collected by the spitting method before and after consumption on the first and seventh days. Examination of lactoferrin levels was done using the Enzyme-Linked Immunosorbent Assays (ELISA). Differences in lactoferrin levels in each group before treatment on day one and day seven were analysed using the Friedman and analysis of variance (ANOVA) tests. Differences in lactoferrin levels between the formula milk and sterilized milk groups were analysed using the independent sample t-test and the Mann-Whitney test (p<0.05). Results: The average levels of lactoferrin before consuming formula milk was 0.212 ± 0.034 mg/100ml and increased to 0.222 ± 0.036 mg/100ml and 0.315 ± 0.026 mg/100ml. In the sterilized milk group, lactoferrin levels increased from 0.216 ± 0.033 mg/100ml to 0.225 ± 0.032 mg/100ml and 0.235 ± 0.027 mg/100ml. The increase in lactoferrin levels was more significant in the formula milk group on the seventh day (p=0.001, p<0.05). Conclusion: Formula milk, which contains whey protein, has a high potential in increasing lactoferrin levels.

From swill milk to certified milk

Industrialization and urbanization jeopardized infant nutrition during the 19th century. Cow’s milk was produced in the cities or transported long distances under suspect conditions. Milk was contaminated with bacteria or adulterated with water, flour, chalk, and other substances. When distilleries proliferated in the metropoles, their waste slop was fed to cows who then produced thin and contaminated swill milk. Following a press campaign in the US, the sale of swill milk was prohibited in 1861. Bacterial counts became available in 1881 and helped to improve the quality of milk. Debates on pasteurization remained controversial. Disposal of the wastewater of millions of inhabitants and the manure of thousands of cows was environmentally hazardous. It was not until 1860 and after several pandemics of Asiatic cholera, that effective sewage systems were built in the metropoles. Milk depots were established in the US by Koplik for sterilized and by Coit for certified milk. In France, consultation services named goutte de lait distributed sterilized milk and educated mothers. Efforts to improve milk quality culminated in the International Congresses for the Prevention of Infantile Mortality.

Features of the Secondary Structure of BSA – Containing Protein Complexes, Isolated from Milk of High Temperature Processing

Present paper describes features of the component composition in the secondary structure of BSA–containing protein complexes isolated from ultra-pasteurized (UHT), sterilized (SHT) and powdered (DRY) milk. We have found β – sheets to present in all complexes investigated. However, the smallest number of such components have been revealed in samples derived from sterilized milk with less β – sheets in 1621–1626 cm–1 region. The composition study of the complexes originated from UHT milk has shown random coils to be the rarest in them. When considering the structure of the complexes isolated from powdered milk, the α – 310 – heliсes were more characteristic for such samples, then the α – helix. Moreover, during spray–drying, the number of random structures increase with a simultaneous decrease in the number of β – sheets, whereas in UHT – and SHT – processing the number of random structures is inversely proportional to the number of α – helices.

Proteolytic Traits of Psychrotrophic Bacteria Potentially Causative of Sterilized Milk Instability: Genotypic, Phenotypic and Peptidomic Insight

The proteolytic traits of the psychrotrophic strains Pseudomonas poae LP5, Pseudomonas fluorescens LPF3, Chryseobacterium joostei LPR1, Pseudomonas fulva PS1, Citrobacter freundii PS37, Hafnia alvei PS46, and Serratia marcescens PS92 were initially investigated by phenotypic and genotypic approaches. Six strains elicited extracellular proteolytic activity, and five expressed the thermostable AprX or (likely) Ser1 enzymes. Then, the strains were inoculated (104 CFU/mL) in microfiltered pasteurized milk and kept at 4 °C for five days. All of the strains reached 108 CFU/mL at the end of storage and five produced thermostable extracellular proteolytic enzymes. The freshly inoculated samples and the corresponding samples at 108 CFU/mL were batch-sterilized (131 °C, 30 s) and kept at 45 °C up to 100 days. The former samples did not gel until the end of incubation, whereas the latter, containing P. poae, P. fluorescens, C. joostei, C. freundii, and S. marcescens, gelled within a few days of incubation. The thermostable proteolytic activity of strains affected the peptidomic profile, and specific proteolyzed zones of β-CN were recognized in the gelled samples. Overall, the results confirm some proteolytic traits of psychrotrophic Pseudomonas spp. strains and provide additional insights on the proteolytic activity of psychrotrophic bacteria potentially responsible for sterilized milk destabilization.

Industrial Practice for Reducing Defective Sterile Milk Products Produced Using Overpressure Rotary Retorts

Indonesian consumers are fond of commercially sterilized milk as indicated by increasing product sales. High demand for products intensifies the need to increase productivity, generally achieved by minimizing product defects. This study aimed to reduce the number of defects in commercially sterilized milk produced using overpressure rotary retorts. Based on Pareto analysis, the percentage of defective products was 5.14% of which 2.37% were dented bottles. A cause-effect diagram (Ishikawa Diagram) was used to find the root cause of dented bottles. The pressure difference between the retort chamber (external pressure) and inside the product packaging (internal pressure), and the number of bottles stacked inside the retort basket (bottle density) were found as major factors for causing dented bottles. The internal pressure was 1.20 bar higher than the external pressure. By reducing the pressure difference to 0.40 bar, the percentage of dented bottles could be reduced to 0.79%. Applying the low-est bottle density (73% of the retort basket area occupied by bottles) during the sterilization process could decrease the number of dented bottles, however, it also increased the appearance of striped lids. The best conditions for sterilization (pressure difference = 0.40 bar; number of bottles/basket = 1938 bottles) which were used in the three-month full-scale production trial reduced the percentage of defective products from 5.14% to 2.24% of which 0.76% were dented bottles. Setting the retort pressure at 2.80 bar could avoid 52,920 defective bottles of commercially sterilized products per month.

Developing a Low-fat Drinking Yoghurt by Incorporating Green Tea (Camellia sinensis) Extract as a Functional Ingredient

Background: Nowadays people are health-concerned and consume more of functional foods. Thus, this study is focused on developing a drinking yoghurt incorporated with green tea (Camellia sinensis) extract as a functional ingredient.Methods: Green tea extract (GTE) was obtained by brewing 02 g of dried green tea leaves in 100 mL of water at 90°C for 30 minutes. Drinking yoghurts were prepared with standardized sterilized milk incorporated with 0%, 10%, 15%, 20% and 25% (v/v) of GTE. Physio-chemical, microbial and sensory analysis were conducted to evaluate the quality attributes of the developed product. It was stored under refrigerated conditions (4°C) for 15 days.Result: Sensory data showed that 25% green tea extract incorporated drinking yoghurt had the best organoleptic properties. It had the significantly (p less than 0.05) highest ash and lowest fat contents compared to the control. Significantly (p less than 0.05) higher pH and lower titratable acidity values were observed in 25% green tea extract incorporated yoghurt compared to the control on 15th day of storage. The microbial analysis did not show the presence of coliform. In conclusion, yoghurt incorporated with 25% (v/v) green tea extract has better organoleptic properties and nutritional value while it can be stored under refrigerated conditions for 15 days without any quality deterioration while producing at affordable price.