Cheese Making Aptitude

Cheese Making Aptitude is a very important technological feature for cheese production. Intermizoo in the latest years has been involved in an intensive research on this trait. First project called “BullAbility” started in 2007 thanks to a collaboration with the research group of Professor Martino Cassandro from University of Padova.
From the beginning we saw the potential application of the Cheese Making Aptitude on the genetic aspect and as tool for improve the whole dairy industry.
In the next paragraphs we will try to give more information about this milk characteristic.

 

 

What is Cheese Making Aptitude?

In general Cheese Making Aptitude, also called Milk Coagulation Properties, can be define as the feature of the milk to react with a clotting enzyme and produce a curd with a suitable firmness in a reasonable time. Cheese Making Aptitude look on coagulation process that is a crucial step on cheese production.
 

The main theory is that a milk has a high efficiency on cheese production if coagulates in short time and reach a strong firmness of the curd. This theory has been proved from several researches started in 1980s (Pecorari e Mariani, 1987; Aleandri et al., 1989; Ng-Kwai-Hang et al., 1989). In this studies they found a higher cheese yield when milk coagulation time was shorter and the curd firmness was stronger, and on the other hand there was less fat and protein lost into the whey.
This occurs because milk that coagulates quickly is able to entrap more casein and fat into the coagulum before it is cut than does slowly coagulating milk.
Moreover in some studies has been found that an inadequate Cheese Making Aptitude can affect the final quality of cheese, the composition, the percentage of discard and defects, and the time and cost for cheese making.
These studies show that Cheese Making Aptitude plays an important role on the cheese making and underline the concept that the classical milk quality parameters such as protein, fat and somatic cell content are not enough for define a suitability of milk for cheese industry.

 

How we measure Cheese Making Aptitude?

The direct analysis for Cheese Making Aptitude is performed by an instrument called Milk coagulation meter such as “Lattodinamografo” or “Formagraph”.
We talk here about direct analysis because like we´ll see in the next paragraphs, is also possible to predict Cheese Making Aptitude parameters by more fast and modern methods.
The direct analysis is anyway the reference method. In this analysis is simulated a real cheese making process where the milk change his phase from colloidal suspension to gel. Is used a 10 mL milk sample warmed at 35 °C and a standard quantity of rennet is added. The instrument checks constantly the consistence of the sample for 30 minutes.

 

Attitudine casearia

Milk coagulation meter

 

This instrument provides a graph where is possible to identify two important parameters:
- Rennet Clotting Time (RCT), which is the time between the addition of the clotting enzyme and the beginning of the coagulation process,
- Curd Firmness (A30), which is a measure of curd firmness derived from the distance of the two curves in the graph at 30 min after addition of the clotting enzyme.

Output graph of milk coagulation properties analysis

Graph produced by a milk-coagulation meter, and the milk coagulation property traits: RCT, rennet clotting time; A30 , curd ?rmness 30 min after addition of the clotting enzyme.
 

 

A milk with optimal Cheese Making Aptitude should coagulate in less than 18 minutes and reach a curd firmness (A30) stronger than 20 mm in the graph.
Some authors reported a general worsening of Cheese Making Aptitude over the year and more and more samples that even don´t coagulate within 30 minutes of analysis.

 

Cheese making trials with separation of cows by Cheese Making Aptitude

Even if there were already international research that show the effect of Cheese Making Aptitude on cheese production, during our research project we wanted to confirm this fact in some specific local cheese productions.
For this purpose we made repeated cheese making processes using milk separated during milking. The milk came from three farms where two groups of cows each farm were previously separated by the individual Cheese Making Aptitude analysis. One group produced milk with “good” Cheese Making Aptitude and the second group “abnormal”. The milk was kept separated and delivered to two dairy industries in Veneto Region, where in one was produced Asiago cheese and in the second Grana Padano cheese. The best performance of milk with “good” Cheese Making Aptitude were very clear in both cheeses.

The chemical analysis of milk used for trials showed about the same level of fat, protein and somatic cells but differed for Cheese Making Aptitude.
For Asiago cheese the milk with “good” Cheese Making Aptitude produced 9.25% of cheese while the milk classified as “abnormal” produced 8.98%. For Grana Padano cheese the difference was even bigger, 8.02% for “good” milk vs 7.45% for the “abnormal”.
The trials confirmed that Cheese Making Aptitude has an effect also in this specific cheeses produced in industrial scale.
We can say that a milk with optimal Cheese Making Aptitude if processed in proper way can produce in average 5% more cheese than milk with “abnormal” quality. If we are using “optimal” milk there are less problems during cheese making process, and will produce cheese with less problems during aging, less incidence of defects, and it can reach more easily excellent quality grade.

 

Prediction of Cheese Making Aptitude by Mid-Infrared Spectroscopy

Like we saw in previous paragraph, the direct way to measure Cheese Making Aptitude with milk coagulation meter is expensive and time consuming and for this difficult to record in all the cow population. A feasible way for the implementation of Cheese Making Aptitude assessment in the phenotypic recoding system has been proposed using mid-infrared spectroscopy (MIRS) (De Marchi et al., 2009; Cecchinato et al., 2009), the same technology already used for the analysis of protein and fat content. This technology is based on the principle that every biological substance has different Infrared light absorbance, like a fingerprint of a specific sample. From this feature is possible to set up a calibration equation from spectral data and a reference methods.


Example of Mid-Infrared absorbance spectra from different samples

Thanks to the research collaboration between Intermizoo, research group of Prof. Martino Cassandro from University of Padova and district of Veneto Region Dairy Industries, has been possible to provide the Veneto Region recording system laboratory with mid-infrared calibration equation for Cheese Making Aptitude. From this point started the phenotypic recording of these traits in Holstein Friesian population and the consequent possibility for bull genetic.
 

Genetic aspects of Cheese Making Aptitude

Cheese Making Aptitude is not a new measure of milk quality, indeed cheese makers know form several decades this analysis for assessment the quality of bulk milk in the dairy.
But only about 15 years ago a research group from Finland published the first genetic results of Cheese Making Aptitude measured at cow individual level. Right after this study, the Italian research group of Prof. Martino Cassandro from University of Padova repeated the trial in the Italian Holstein and found very interesting data.
The results showed that Cheese Making Aptitude traits has quite good heritability, similar or higher that other production traits like milk yield and protein and fat content.

The results showed also a moderate genetic correlation with other classical milk quality parameters like milk content and somatic cell count, but this relation is not strong enough to replace the information of Cheese Making Aptitude analysis and use an indirect selection.
Moreover has been found a moderate relationship with milk protein genotypes like k-casein or beta-lactoglobulin, where the best performance for Cheese Making Aptitude were for the alleles consider favourable also for cheese production (like B for k-casein or B for beta-lactoglobulin). But the effect of protein genotypes explain only a portion of Cheese Making Aptitude variability and they can help to improve it but not substitute the direct information.
So the Cheese Making Aptitude is a new trait of cow genetic that give more precise information about milk quality suitable for cheese making and is a valid tool in order to improve dairy industry efficiency.

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