After reading Chemistry in Your Kitchen by Matthew Hartings this summer I decided to see if my International Baccalaureate students would be willing to have my learn how to cook a dish with their families. Periodically my students will have a potluck during their core days where they miss their classes all day working on external assignments and there tends to be a wide variety of international cooking on display.
In October I met with my first family (thank you Sharmas!) to learn how to cook Paneer. I have grown up as a very picky eater and when you are a child that is a picky eater it becomes the mission of a select few to get you to try their casserole. So I was very excited about paneer since it seemed like the perfect dish that was both new but not overwhelming to me.
We boiled a very large quantity of milk and added some lime and vinegar to curdle the milk when it was just reaching boiling temperature.
Figure 1: Milk just before boiling
Figure 2: The milk curdling after the addition of lime juice and vinegar
The acid bonds to phosphate groups on the casein proteins. The casein has a hydrophilic and hydrophobic end. The hydrophobic ends attract the same portion of other casein proteins and the hydrophilic ends attract to water because of the negative charge of the phosphate groups. The acid reduces the attraction to water and causes the casein to clump as seen in Figure 2. The mixture is then put into a towel allowing the excess liquid to drain. The protein along with some trapped fats then link forming a block of paneer.
Figure 3: The paneer mixture is now forming while the excess liquid drains
Figure 4: The paneer takes shape and can be cut into pieces
At this point we made a curry sauce using a variety of spices, tomatoes and onions. The paneer was added to the curry sauce.
Figure 5: Paneer cooked in curry sauce
Figure 6: The complete meal with paneer, lentil soup, yogurt, salad and naan.
I had disorganized intentions behind doing this. I had personal desires to learn how to cook more foods, and connect better with students and families in our IB program. I had professional desires to connect chemistry and cooking and also chemistry with international mindedness. The experience surpassed my expectations. I learned about my students, got to eat an authentic Indian meal and it was completely vegetarian. I learned you can purchase paneer at Costco and I also learned where to buy spices and groceries for preparing Indian food. The concepts in this dish applied perfectly to the unit we learned next in class about acids and bases and we cooked paneer in class to reinforce the concept of acids as well as allow more students to experience an international dish. We used citric acid rather than vinegar and it worked fine with no negative impact on the taste of the paneer. Future possible experiments could focus on how the pressure applied to the cheese as it forms influences the final product or how concentration of acid affects the final product. I believe the proteins clumping causes various components of the mixture including fats to get trapped and both of these experiments should influence what and how much gets trapped. It would also be interesting to move a step further and add rennet and start developing cheeses.
Figure 7: My students Manasi and Ritika along with Manasi's sister Tanvi after our meal