Effect of high hydrostatic pressure and heat treatment on antimicrobial protein stability, shelf-life, and rheological characteristics of donkey milk

2021-11
Köker, Alperen
Show full item record
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
469
views
256
downloads
Donkey milk has been gaining popularity due to its beneficial properties and similarity to human milk, however, since heat treatment lead to phase seperation and nutritional losses, it is consumed raw, which may cause health risks and limit its shelf life. High hydrostatic pressure (HHP) is a non-thermal food processing technique in which microbial inactivation can be obtained with minimum effects on fresh like properties of food product. This study aimed to investigate the effects of HHP, and heat treatment on physicochemical and rheological properties, stability of proteins, microbial load, and shelf-life of donkey milk. Increasing processing pressure (200, 400, and 500 MPa) decreased microbial load, lysozyme, and lactoferrin contents significantly (p<0.05). Although HHP application temperatures of 25 °C and 35 °C had no significant effect (p>0.05) on microbial load, lysozyme, and lactoferrin loss, while at 45 °C, decreased these parameters significantly (p<0.05). By using different processing times similar values were obtained (p>0.05) in terms of microbial inactivation, lysozyme, and lactoferrin content. Even though heat treatment of donkey milk samples at 75 °C for 1 and 2 min resulted in sufficient microbial inactivation, high lysozyme and lactoferrin inactivation were observed. Total aerobic mesophilic bacteria (TAMB) counts of HHP-treated and heat-treated milk samples stored at 4 °C exceeded 5 log CFU/mL after 21 days of storage, in contrast to untreated milk stored at 4 °C in which TAMB count increased to 5.82 log CFU/mL after 7 days of storage. pH values were decreased and titratable acidity values increased within the storage period for all samples. Significantly higher flow consistency index (K) and significantly lower flow behavior index (n) were observed in heat-treated samples comparing with untreated and HHP-treated samples (p<0.05). The results suggest that HHP is a more suitable process than heat treatment for treatment of donkey milk since lower loss of valuable antimicrobial proteins with longer shelf-life is obtained by HHP.
Donkey milk, High hydrostatic pressure (HHP), Antimicrobial proteins, Microbial inactivation, Shelf-life
https://hdl.handle.net/11511/94948
Graduate School of Natural and Applied Sciences, Thesis

Suggestions

Effect of high hydrostatic pressure on physicochemical and biochemical properties of milk
Altuner, Ergin Murat; Alpas, Hami; Erdem, Yasar Kemal; Bozoglu, Faruk (Springer Science and Business Media LLC, 2005-10-6)
Interest in high hydrostatic pressure (HHP) applications on milk and dairy products has recently increased as HHP offers a new technology for food preservation to the food industry. Although HHP-induced microbial destruction, rennet or acid coagulation of milk and increase in cheese yield has been reported, the actual effect of HHP application on milk constituents still remains to be unexplained. Therefore, we have analyzed the effect of HHP on physicochemical and biochemical properties such as turbidity, p...
Effect of high hydrostatic pressure on the functional properties of soy protein isolate
Zengin, Kübra; Alpas, Hami; Department of Food Engineering (2022-2-11)
Soy protein is a low-cost additive with high biological value, unique functional properties, and beneficial effects on health, and it is widely used in the food industry as an important ingredient. When the health and functional properties of soy protein are considered altogether, there are several benefits for consuming and using it in foods. High hydrostatic pressure (HHP) is a non-thermal novel processing technology that has been generally used to destroys vegetative cells, microorganisms and enzymes. Ad...
Effect of high hydrostatic pressure (hhp) on the quality parameters and shelf life of acidified protein drink
Tırpancı, İrem Bige; Alpas, Hami; Department of Food Engineering (2022-2-11)
Acidified milk drinks (AMD) has recently gained popularity due to their nutritional aspects. Most of these drinks suffer from sediment formation and wheying off during shelf life and in order to prevent it, hydrocolloids such as pectin is used as stabilizers. It is important to have a stable beverage without sacrificing milk protein content. Moreover, having an alternative pasteurization method such as High Hydrostatic Pressure (HHP) rather than a thermal treatment could also be a better choice to protect n...
Microbial Control of Milk and Milk Products
Guzel, Mustafa; Soyer, Yeşim (2017-01-01)
Milk has been the one of the main nutrient sources of human diet for centuries. Microbial studies on milk date back to the seventeenth century, when Kircher used a microscope, and observed the minute worms in milk. Two centuries later, in the1850s, Pasteur proved that the spoilage of milk resulting the sour taste was caused by microorganisms. Pasteur's discoveries on the effect of heat on undesirable microorganisms in beer and wine opened a new era in food science. Therefore, the process was named "pasteuri...
EFFECT OF THE LACTOPEROXIDASE SYSTEM ON THE ACTIVITY OF STARTER CULTURES FOR YOGURT PRODUCTION
Basaga, H.; Dik, Tunay (VOLKSWIRTSCHAFTLICHER VERLAG, 1994)
The LP system in raw milk was activated by the addition of equimolar concentrations (0.25 mM) of hydrogen peroxide (H2O2) and thiocyanate (SCN) as KSCN and utilizing the inherent milk lactoperoxidase (LP). H2O2 and SCN- concentrations were determined during the experiments by using spectrophotometric methods and found to decrease to 1.5 mug/ml and 0.4 mug/ml respectively in 5 h. A relatively small amount of H2O2 was produced in the untreated milk which then was found to decrease. The activated sample, at th...
Citation Formats
A. Köker, “Effect of high hydrostatic pressure and heat treatment on antimicrobial protein stability, shelf-life, and rheological characteristics of donkey milk,” M.S. - Master of Science, Middle East Technical University, 2021.
METU IIS - Integrated Information Service open@metu.edu.tr