Gelling properties of milk gels using rennet as a coagulant

Abstract

As the consumption of dairy is a common staple in the Nordic and European diet and culture, better understanding of the dairy industry as a whole, and especially the cheese industry is needed to aim for a more sustainable production. This project aims to offer an extended approach on the rennet coagulation of milk, analysing the gelling properties of skim milk samples at different pH values (5.5-6.7) with various additions of CaCl2 (1.0-10 mmol/L), as well as the impact of the presence of fat and the fat content (2%-3%) of the milk samples.
Two trials were performed during this project, the Response Surface method trial, and the Effect of fat on gelation-trial. The Response Surface method trial contained skim milk samples with a varying degree of added CaCl2 at different pH, to investigate how pH and CaCl2, and the interaction of these factors affect the gelling properties of the skim milk. The Effect of fat on gelation-trial contains both skim milk and full fat milk samples, with varying fat content (2%-3%), to establish if the fat content, or the presence of fat had a significant impact on gelling properties of the milk. Methods used in order to measure the gelling properties of the milk samples during these trials include Rheometer to establish G’ at 30 min, Turbiscan to establish the Δ Back Scatter (ΔBS) and Malvern Master sizer to establish particle size. Statistical methods such as Minitab21 and its response surface method was used to not only plan the Response surface method trial, but also to generate contour plots, pairwise parson correlations and 2-Sample T-test. Matlab was also used to generate plots of gelation curves.
The results concluded that pH is an important factor regarding gelling properties of rennet milk gels, as it had a significant effect on both gelation time and G’ 30 min. CaCl2 does not have a statistically significant effect on the variables of gelation time, G’ 30 min and ∆BS 30 min. The fat content and the presence of fat had no significant effect on the gelation time, G’ at 2x gelation time and G’ 30 min, while the fat content had a significant effect on the ∆BS 30 min. It was expected that the pH would be significant for gelling properties, but unexpected that CaCl2, fat content and presence of fat did not have a bigger impact on the results obtained. In order to verify the results presented in this report, more research and trials, especially on the impact of fat content, presence of fat and CaCl2 needs to be made.

Popular Abstract

How does the pH, fat content and addition of calcium chloride effect gelling properties of milk gels?
pH, calcium chloride and fat content are all factors with an integral role in the cheese making process, or is it so? By understanding these factors and their significance for the milk gel formation, steps are taken towards a more sustainable and knowledgeable production that the dairy industry is in desperate need of.
Cheese, and dairy products in general have been around for a very long time, albeit in more simple forms than the products available in the grocery store today. But now over 8000 years later, fermented milk products are still a staple in the Nordic and European diets. As the call for more sustainable food production becomes louder, and introduction to plant-based version of beloved dairy products are growing by the dozen, the dairy industry needs to act and not only take responsibility of their environmental impact, but also to implement change. But how would this be possible? “With great power comes great responsibility”, a quote most commonly known from Marvels the Spider-Man comics, but something that should be taken to heart by everyone, as it is the responsibility, and burden of the people today, to ensure a better future for tomorrow.
In order to instill change in any production process, a deep knowledge of said process and its components is crucial. During the production of cheese, the incoming milk goes through a pre-treatment, where the milk is pasteurized, and spores are removed. It is then centrifuged and standardized to achieve the right fat content. It is here that lactic acid bacteria, or lactic acid is added in combination with calcium chloride and rennet to achieve coagulation of the milk. It is through the coagulation of the milk that a gel network consisting of casein micelles and fat globules can be created, that lays the foundation for remaining steps of the cheese making process. The gel is then cut, pressed, salted and ripened to finally be available for consumers to purchase.
Having a deeper understanding for how the fat content of the milk used during coagulation and gel formation affect the final gel properties, but also the impact of pH and addition of calcium chloride, makes it possible to assess the effect and necessity of these factors. Perhaps the addition of calcium chloride can be minimized or even removed, as its contribution of gel properties are minute? This would in turn render the process more streamlined and even more specialized to certain types of cheese.

• author: Voicu, Dragos and Bengtsson, Elin
• supervisor: Frida Lewerentz; Maria Glantz
• organization: Food Technology and Nutrition (M.Sc.); Biotechnology (MSc)
• course: KLGM01 20221
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: gelation, rennet, milk, food technology, biotechnology
• language: English
• additional info: KLGM10 – Examensarbete i Livsmedelsteknologi – Civilingenjörsutbildning i Bioteknik; KLGM01 – Degree Project in Food Technology – Master’s in Food Technology and Nutrition
• id: 9086663
• date added to LUP: 2022-06-13 09:34:13
• date last changed: 2022-06-15 15:29:35