Effect of Indirect and Direct Heat Treatment on Nutritional and Technological Properties of Milk

Abstract

This research was done to analyse how different heat treatment processing conditions influence the properties of milk. The focus was on high temperature heat treatment, namely extended shelf life (ESL) and ultra-high temperature (UHT) milk. The milk processing was performed in the range of 124 - 143 ℃ for 1 and 4 seconds. The analyses that were done involved nutritional and technological properties. Technological properties involved pH, particle size distribution, stability, colour, and ionic calcium. The analyses on nutritional properties comprised fat, protein and lactose composition and it showed no impact of heat treatment on these components of milk. Furthermore, the pH value was not significantly influenced by different holding temperatures or times. However, the type of system played a role; in direct systems, an increase in pH value was observed in heat-treated samples when compared to low pasteurised milk. This was not true for indirect, where heat treatment led to a reduction of pH. Regarding particle size analyses, no significant changes occurred during indirect heat treatment. This includes no significance of holding temperature or time on particle size distribution. However, an increase in particle size was observed in the direct system, caused by fat and protein aggregates. This is normally prevented by using a homogeniser downstream which was not done in this experiment. Colour was slightly changed after heat treatment. However, it was not recognized visually. Flocculation was observed after heat treatment. Ionic calcium concentration was decreased in the end product. Storage analysis at 4℃ for 4 weeks showed no significant changes in pH, stability, and colour.

Popular Abstract

Heat Treatment: The Good Way to Preserve and Keep the Quality of Your Milk

Are you a milk lover who is interested in the changes of milk during heat treatment? And looking for the best treatment to preserve the quality of your milk? Or you just might be curious if the high-temperature heat treatment has a negative effect on your milk. Let us find out!
Milk is a widely consumed product around the world which contains vital nutrients that play a role in human body development. It is the starting material of many beloved products such as cheese, butter, yoghurt and ice cream. To make these products, the milk has to be processed, and one of the most common techniques that ensure safe-to-consume milk is heat treatment. With a growing demand for food worldwide, manufacturing companies are growing rapidly and increasing their production rate. This led to an advancement of technology and the development of processing techniques to ensure the long shelf life of milk, even at room temperature, so-called ultra-high-temperature (UHT) milk. However, high temperatures can result in undesired changes in milk, such as its colour, taste, or molecular structure. This is why choosing optimal heat treatment conditions that ensure all the benefits with minimum negative consequences on the product is essential.
This research will analyse just that; how the different time and temperature combinations and heating systems influence the final product. The heat treatment can be done with two systems, indirect and direct. Indirect is more commonly used in the industry because of a good balance of cost and performance. In contrast, the direct heat treatment is expected to produce a product with fewer negative changes in milk while providing the same benefits of increased shelf life. Another processing parameter is the time and temperature of heat treatment, and this research focused on milk processed at high temperatures, extended shelf life (ESL) and ultra-high-temperature (UHT) milk. Overall, the analyses showed that high-temperature heat treatment had no significant negative influence on the technological properties of milk.
The analyses on stability indicate any separation of milk or a formation of creaming, and particle size distribution tells us whether any complexes of fat and protein particles occurred. However, any changes in these properties during heat treatment can be balanced with a homogeniser that breaks up large particles and improves the stability of milk. When comparing the two heating systems on how they impact milk, the differences were only observed regarding particle size distribution and stability during 30 days of storage, with more significant changes in direct. Other analyses on fat, protein, and lactose composition showed no changes after heat treatment. Similarly, the pH value and the colour were not significantly influenced. This indicates that no chemical reactions that cause a breakdown of fatty acids or an increase of organic acids in milk occurred. To summarise, all the heat treatment conditions tested in this project did not impact the milk negatively. Even the changes observed in direct heat systems regarding particle size and stability during storage can be balanced out with homogenisation, as is commonly the practice in the industry, for the same reason.

• author: Babic, Marja and Madina, Prilliani
• supervisor: Shruti Lalwani; Maria Glantz; Frida Lewerentz
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM01 20231
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: milk, UHT, ESL, indirect heat treatment, direct heat treatment, nutritional content, technological properties, storage analysis, food engineering
• language: English
• id: 9122390
• date added to LUP: 2023-06-13 10:10:46
• date last changed: 2023-06-13 10:11:33