Homogenization of yoghurt milk

Abstract

Yoghurt is a dairy product that is well known around the world. When producing yoghurt, the homogenization process is one of the most energy demanding steps. In order to decrease the energy consumption the aim of this master thesis was to understand if the homogenization pressure, the homogenization temperature and the positioning of the homogenizer (upstream or downstream) affect the quality of the final yoghurt.

When the yoghurt milk is homogenized, the fat globules are disrupted into smaller fat globules and are easier incorporated into the yoghurt gel. The gel formation in yoghurt is a complex process since the gel is sensitive to temperature changes, concentration of culture and vibrations during formation among other things. It is well known that homogenization of milk improves the storage stability and with this thesis, it was of interest to investigate if a partial homogenization of yoghurt milk would contribute to the same quality improvement.

From the project, no effect of homogenization pressure on the proteins and the quality of the yoghurt could be found. This would mean that partial homogenization of yoghurt milk would be possible without compromising the quality. Another conclusion was that the higher homogenization temperature led to a decrease in the fat globule size but none of the quality parameters nor the sensory analysis showed to be affected by the temperature change. This project also showed that there was an indication of the upstream homogenization process to be preferred.

Popular Abstract

Several process steps are necessary to produce yoghurt but what if one of the most cost demanding steps could be improved and still result in a product with a high-quality value? This project showed that the parameters such as pressure and temperature of an essential but expensive part of the production can be changed without compromising the quality.

Yoghurt is one of the most famous dairy products known. It is produced of milk which is referred to as yoghurt milk when it is intended to be used for yoghurt production. The yoghurt milk itself contains different components such as fat and proteins that influence the yoghurt structure. The yoghurt is produced by adding a culture to the milk which gives the yoghurt its characteristic properties such as aroma, taste and texture. Because of its popularity on the market, it is of great concern that the process is as low cost demanding as possible and contribute to a product with high quality in both an industrial and a consumers point of view.

The yoghurt milk passes different process equipment before the yoghurt is produced, one of these are the homogenizer. The homogenizer decreases the fat globule size in the milk and this is essential to obtain a high-quality product. The homogenizing parameters, pressure and temperature, are affecting the outcome of this process step. Some investigations have also shown that the proteins in the milk were affected at higher pressures than used for producing yoghurt milk. If the proteins would not be affected by the pressure used in the yoghurt milk production, then a minor amount of milk would be necessary to homogenize, and this would lead to lower homogenization costs.

Two different processes have been used in the project to investigate how the quality parameters texture, viscosity and syneresis are affected by the homogenization pressure, temperature and position. The batch process was performed at the Food Technology´s pilot production plant at the Department of Food Technology LTH. This process contained some manual steps where the continuous process was similar to an industrial production regarding holding times and capacity of the homogenizer. The continuous process was performed at the Product Development Centre at Tetra Pak.

The yoghurt milk was either acidified with a culture or an acidifying agent called glucono-delta-lactone. The culture was used to be able to perform sensory evaluations to obtain information about the consumers perception of the yoghurt. Glucono-delta-lactone generates the desired decrease in pH but does not contribute to the specific yoghurt taste and was used to study the possible effects of using different homogenization temperatures and pressures.

The homogenization pressure and temperature have been varied to see how they affect the final yoghurt quality. From quality analysis such as texture and viscosity as well as sensory evaluations, it could be stated that using a lower homogenization pressure and a higher homogenization temperature would not give any noticeable quality change. Regarding the position of the equipment in the process, an indication that an improvement of the consistency coefficient could be noted if the homogenizer was positioned before the holding cell.

The project has gained information about how the homogenization parameters pressure and temperature as well as its position affects the texture and viscosity of the yoghurt. This knowledge can further be used and lead to cost effective solutions without changing the quality on a noticeable level.

• author: Samuelsson, Jessica and Lindberg, Sofia
• supervisor: Andreas Håkansson; Maria Glantz
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLGM10 20181
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: food technology, livsmedelsteknologi
• language: English
• id: 8948949
• date added to LUP: 2018-06-18 14:40:48
• date last changed: 2018-06-18 14:40:48