Coagulation Properties of Swedish Red Dairy Milk: Effect of Poor-coagulating Milk, Pasteurization and Fat

Abstract

Rennet coagulation ability of milk is of utmost importance in cheese manufacturing industry since it is directly related to cheese quality and yield, then translated into economic benefit. This study examined the rennet coagulation ability and composition of milk from individual Swedish Red (SR) cows, the second most common dairy breed in Sweden. Additionally, the study explored how the presence of poor-coagulating (PC) milk in farm tank milk could affect rennet coagulation properties. The influences of pasteurization and milk fat on milk rennet gelation were also investigated. Milk samples from 64 individual cows were evaluated for gelation properties at 32oC for 40 minutes employing two simultaneous techniques, small amplitude oscillatory rheology and multiple light backscattering. The result indicated that 15.6% of the SR cows produced PC milk. A comparison between PC milk and normal coagulating milk showed no significant difference in milk properties including composition, free ionic calcium, pH and casein micelle size. But the rate of aggregation was significant different between the two groups. Normal coagulating milk exhibited a rate of aggregation three times greater than PC milk. Protein was the only compositional trait positively affecting rennet coagulation properties while casein micelles size influenced the rate of aggregation of milk samples having normal gelation ability. Blending PC milk with dairy tank milk impaired the coagulation properties of the tank milk, with the deterioration effects were proportional to percentage of PC milk . However, the mixture containing 75% (w/w) PC milk and 25% (w/w) farm tank milk exhibited satisfactory coagulation ability which did not fall into PC milk group, showing that 25% of tank milk had ability to counteract the deterioration caused by PC-milk. The heat treatment of tank milk at 63oC for 30 min compromised rennet coagulation properties compared to raw milk, with significant differences in rheological properties. The presence of milk fat in full fat milk sample also resulted in slightly poorer coagulation characteristics than its skimmed milk , the absence of milk fat increased final gel strength and rate of aggregation.

Popular Abstract

Understanding Rennet-indued Coagulating properties of Milk: A Foundation for more Sustainable Cheese manufacturing.
Milk is the primary ingredient in cheese production, a favourite food enjoyed worldwide. Did you know that coagulation of milk with coagulant rennet is the first step in making cheese, transforming milk from liquid into semi-solid state called milk gel? This gel is then cut to expel liquid, so-called whey, with the remaining solid part pressed, moulded, and processed into cheese. Thus, to produce 1 kg cheese a more than tenth times amount of milk needed, 10 – 12 kg. In Sweden, the second most common dairy breed is Swedish Red (SR) with a huge amount of milk goes to cheese manufacturing annually. Under manufacturer perspective, milk should have good gelling properties to ensure economic benefits. Interestingly, cheese is never commercially made from the milk of a single cow; instead, it is produced from milk pooled from many cows. Understanding the coagulation properties of milk at the individual cow level can support a more sustainable cheese industry. That’s where this research comes in. So, are you curious about how gelling ability of individual cows are? Follow me and figure it out!
This research will basically analyse rennet coagulation properties of milk from individual SR cows and factors affecting these properties. Parameters such as gelation time, gel strength, and firmness are evaluated, classifying milk samples into groups based on coagulation ability, such as good, poor or others. A comparison is also going to be made to see whether there is anything differs between the groups and might be causes of the differences. The analysis showed that 15.6% of the 64 cows produced milk with poor coagulation properties, while the rest had normal rennet coagulation ability. There was no significant difference in fat, protein, lactose, and other milk properties between the two groups, suggesting that the cause of poor-coagulating (PC) milk might be something else such as genetical factor. The analysis also showed that protein affects rennet gelation time, gel strength and firmness of coagulating milk samples.
Since cheese manufacturing involves milk from various cows with different coagulation abilities, the milk undergoes pre-treatment, including pasteurization and fat adjustment. Thus, several additional analyses will be done in this study including the effects of blending of poor-coagulating (PC) milk with farm tank milk, effects of pasteurization and milk fat on milk coagulation. The analyses showed that PC milk impaired the coagulation properties of the farm tank milk, with the negative effects proportional to content of PC within the mixture. Pasteurisation slightly compromised rennet coagulation of milk by taking longer gelation time and producing lesser gel strength compared to raw milk. Full fat milk also exhibits slightly poorer gelling properties than its skimmed milk.
To summary, all the analyses carried out considered both scientific and industrial aspects. Further research should explore the possible causes of poor-coagulation ability of milk from SR individual cows, as well as possibility of improvement such poor characteristics. By that way, the better understanding rennet coagulation of milk can be gained, the brighter future, the more sustainable Swedish and international cheese manufacturing can be achieved!

• author: Vu, Thi Kieu Van
• supervisor: Frida Lewerentz; Maria Glantz
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM02 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: rennet-induced coagulation properties, individual Swedish Red Dairy cattle, milk composition, poor-coagulating milk blending, pasteurization, milk fat, Food Engineering Nutrition and Food Chemistry
• language: English
• id: 9164607
• date added to LUP: 2024-06-18 11:36:20
• date last changed: 2024-06-18 11:36:20