Cheese is a very varied group of food product which is a driver of the fast-food industry across the globe. Ripening is one of the integral process involved in the manufacture of ‘ripened’ variety of cheese such as Swiss (Emmental), Cheddar etc. During the ripening of cheese, there occurs a series of various biochemical and microbial compositional changes which convert bland cheese into desirable cheese with magnificent aroma and taste.
Need For Accelerated Ripening of Cheese
All of these natural pathways are slow and take a considerable amount of time. Therefore, it is quite uneconomical and not only locks up invested money but also adds the production cost (due to refrigeration and air conditioning). Also, slow flavour development and low flavour intensity in the finished product are arising problems with fat-reduced cheeses. So, several promising technologies have been employed in the cheese industry to overcome the drawbacks of conventional methods of cheese manufacture.
What is ripening in the first place?
Ripening at a glance can be termed as a complex process which involves a series of microbial and chemical reactions which are responsible for developing a typical sensory profile of cheese. Microbial changes include the death of starter cells followed by the development of non-starter microflora. Chemical changes involve hydrolysis of casein matrix, change in pH and water binding capacity of curd. Ripening can be understood by sorting changes into two categories i.e. primary and secondary changes.
Primary changes include metabolism of residual lactose (as most of the lactose is lost in whey expulsion), lactate metabolism, proteolysis (protein degradation) and lipolysis (lipid/fat degradation). These primary changes account for developing texture and flavour in cheese. Secondary changes occur simultaneously like degradation of peptides into small peptides and amino acids.
The conventional methods of cheese ripening are time as well as space consuming, cumbersome and energy intensive. So, methods and techniques to accelerate cheese ripening are now extensively used.
Methods of Accelerated Cheese Ripening:
The accelerated methods of cheese ripening can be broadly divide into following two categories:-
- Addition of biological agents
- Addition of exogenous enzymes
- Addition of adjunct cultures
- Use of genetically modified starter culture
- Technical manipulation in manufacturing techniques
- Use of elevated temperatures for ripening
- Use of high pressure treatment
Addition of Biological Agents
Addition of biological agents involves the addition of exogenous enzymes, adjunct cultures and genetically modified starter bacteria. The potentially useful enzymes like ‘Proteases’, ‘Lipases’, etc can be added exogenously for hastening up enzymatic ripening. The study has shown that the addition of fungal proteases and lipase to Cheddar cheese has reduced ripening time by 50%. Adjunct cultures are selected strains which enhances flavour and provide various other benefits. Adjuncts of thermophilic lactobacilli are commercially available. Attenuated starters / lyophilised / mutant starters are added to increase the number of starter bacteria without increasing lactic acidity to achieve the aim of increasing proteolysis.
Technical manipulation in manufacturing techniques
Technical manipulation in manufacturing techniques can also solve the purpose of reducing ripening time. Generally, cheese is ripened at uniform temperature and humidity as per its variants.
For example, in Emmental cheese temperature is set in the range of 22-24°C. This temperature is maintained for 4-5 weeks followed by transferring cheese to a much lower temperature (like 4°C). Such methods are easy and cost-effective. Applying high-pressure treatment to cheese considerably enhances enzymatic reactions and inactivate microbes. This application increases moisture and pH and further affects proteolysis. Irrespective of size and geometry this treatment is uniformly distributed and aids in various biochemical reactions.
Cheese slurries possessing strong cheese flavour have been prepared and added to milk or bland curd to hasten to ripen. These are better suited for preparing processed cheese.
However, the lack of accurate information on the main flavour generating reactions is hampering efforts in this approach. Considerable in-depth information of cheese chemistry is now becoming available which will be useful in genetic engineering of cheese starters.
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Student, Maharana Pratap University of Agriculture and Technology
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