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Chef Tucker Bunch takes stock of culinary techniques and tradition

Working with scientists at U.C. Davis, CIA Chef Instructor, Tucker Bunch has collected data on the effects of different cooking regimes on the physiochemical and sensory properties of chicken stock.

Preparing stock is a fundamental culinary skill that adds value to bones and meat trim that would otherwise be discarded. As a base for sauces, soups and cooking liquids for grains, vegetables, and meat, the flavor, clarity and body of stock can be integral to the overall quality of a restaurant's menu. Despite this foundational role in culinary training, the effects of stock preparation methods on its sensory and physiochemical properties have not been well documented.

Chef Bunch prepares stocks in triplicate to allow for statistical analysis of the results; sub-samples were taken to U.C. Davis for chemical analysis.


This gap in the culinary knowledge base was the point of inquiry for Chef Bunch who decided to collaborate with food scientists to better understand how the science of stock making all boils down. Through the MRFDI he received funding for a research project to measure effects of different starting and cooking temperatures on the color, clarity, texture, protein, mineral content, and liking of chicken stock. This collaborative work between chef and UC Davis post doctoral fellow at the Robert Mondavi Institute has generated an extensive amount of data, some of which challenges the culinary wisdoms that have been handed down over the years.

Four types of stock were prepared in the CIA Greystone's William's Center Kitchen

  1. cold start, cooked at a simmer (99°C)
  2. cold start, cooked at 85°C
  3. hot start (99°C) cooked at a simmer (99°C)
  4. hot start (85°C) cooked at 85°C

Assisted by Dr. Krasnow, Chef Bunch prepared each of the 4 types of stock in triplicate to allow for statistical analysis of the data.

Chef Bunch found that starting temperature did not seem to have significant effect on clarity or protein content of the finished stock. However, the higher cooking temperature did increase the total amount of solids and protein content extracted from the bones and aromatics. As might be expected, viscosity (as measured by rheometer) increased in samples that were cooked at higher temperatures. Sensory tests indicated that the stocks cooked at higher temperatures were preferred over the low temperature stocks.

A "protein gel" or polyacrylamide gel electrophoresis - a type of molecular sieving technique that can separate protein molecules in stock based on their size. An electrical charge pulls the proteins in the direction of the dashed arrow, through the gel. The smaller proteins move farther than the larger proteins. The numbers on the left of the gel indicate the size of the proteins, in kilodaltons (kDa). The blue dashes are actual proteins from the stock samples. Their weights are approximately 35 kDa (similar in size to a protein called myosin). This gel shows that proteins from the different stocks were similar in size.

The next step in this project is to conduct descriptive analysis tests to determine the "drivers" of the preferences for stocks, and whether viscosity plays a significant role in this perception of flavor. Descriptive analysis techniques involve a panel of chefs who will train together to analyze the stock samples with extreme attention and detail. Using flavor standards, they will collectively calibrate their palates, and become specialists of chicken stock flavors, allowing them to taste and evaluate them "blind".

These objective and precise methods for evaluating flavor, composition, and culinary techniques will provide valuable information for product developers who want to create culinary quality products for the retail or the food service sector. For culinary educators, it provides insight into the underlying mechanisms and rationale for one of the culinary fields most celebrated traditions.