With the holidays quickly approaching and along with them massive meals that often leave leftovers in their wake, IFT member Guy Crosby, PhD, CFS, Science Editor, America's Test Kitchen, Adjunct Professor, Department of Nutrition, Harvard School of Public Health, offers tips on safely savoring food the second time around.
Q: Why do leftovers often taste better the next day?
A: Generally because chemical reactions continue to take place that produce more and/or new flavor molecules. Some flavor enhancement may involve the breakdown of proteins to release amino acids such as glutamate and small nucleotides that interact to enhance savory, meaty umami taste, or reaction of amino acids with sugars to produce new flavor molecules by the Maillard reaction (browning), which can occur when the leftovers are reheated.
Q: Is it okay to put hot food directly into the fridge?
A: It is recommended not to place hot foods in the refrigerator because it can warm the refrigerator above 40 degrees Fahrenheit where harmful microorganisms can grow. Plus, if the food is very hot it may take significant time for the food to cool below 40 degrees Fahrenheit giving time for unsafe microorganisms to grow in the food. It is best to let the food cool to 80-90 degrees Fahrenheit before placing in the refrigerator.
Q: What determines how long a leftover meal will last?
A: Two factors, the eventual growth of harmful microorganisms and the development of off-flavors and unacceptable texture. The growth of microorganisms is dependent on the temperature of the food, its moisture level, and the pH level of the food. Acidic pH slows or retards the growth of microorganisms so acidic foods like tomato sauce will generally last longer than a food with a pH above 4.6, such as meat. At pHs below 4.6 bacteria are much less likely to grow. Each food is different. But it’s best to reuse leftovers that have a pH above 4.6 and high moisture within 3-4 days if refrigerated. If in doubt, or if the food will not be reused within 4 days then freeze the food, which stops the growth of microorganisms.
Q: What is the best way to store leftovers?
A: Most leftovers can and should be frozen if they will not be reused within three to four days. Even raw egg yolks can be frozen and reused if a small amount of concentrated sugar syrup is added to prevent damage to the proteins.
Q: If a package of ground beef says that it should be used by a certain date and then you cook it, how many days longer will it last in the fridge?
A: It is probably best to reuse the leftovers within three to four days because ground beef is a high moisture food with a pH above 4.6. One additional day will probably not be too risky for many leftovers, but it is best to use cooked ground beef within four days or less as recommended by the USDA.
Q: How can you reheat leftovers that will have a similar taste and texture as to when they were first cooked?
A: Quickly reheating in a microwave is best for most foods, although microwave ovens can heat food unevenly. Warming up in an oven may be acceptable for some foods like a baked potato, and reheating in a pan also works for liquids like soups. If in doubt use the microwave.
Q: How does cooling down change the flavor of a food?
A: Cooling food changes the flavor in two ways:
Q: Is it safe to refreeze previously frozen leftovers?
A: Yes, as long as the food was not left at room temperature for more than two hours during the first re-thaw, which gives time for harmful microorganisms to grow before the food is refrozen.
Q: Why does citrus keep foods like apples and avocados from browning?
A: Browning of apples and avocados is due to an enzyme called polyphenol oxidase (PPO), which catalyzes the oxidation of polyphenols present in apples and avocados (and raw potatoes) forming brown pigments. The PPO enzyme is much less active at acidic (low) pHs, so the rate of oxidation is greatly slowed. The enzyme is also deactivated by heat.
Source: Guy Crosby, PhD, CFS, Science Editor, America's Test Kitchen, Adjunct Professor, Department of Nutrition, Harvard School of Public Health
Family restaurant owner Dane Carder navigates the hurdles to bring his grandfather’s spaghetti sauce to U.S. grocery stores
A look at trends in the refrigerated foods category.
A description of three new products available to consumers.
Culinary adventures, ultra-convenience, and high-performance health are poised to drive purchases in the center store in an uncertain economic climate.
This column reviews USDA FSIS’ proposed comprehensive strategy to control Salmonella in poultry and reduce the number of associated foodborne illness outbreaks, including declaring the pathogen an adulterant in some chicken products.
Family restaurant owner Dane Carder navigates the hurdles to bring his grandfather’s spaghetti sauce to U.S. grocery stores
A look at trends in the refrigerated foods category.
A description of three new products available to consumers.
Culinary adventures, ultra-convenience, and high-performance health are poised to drive purchases in the center store in an uncertain economic climate.
This column reviews USDA FSIS’ proposed comprehensive strategy to control Salmonella in poultry and reduce the number of associated foodborne illness outbreaks, including declaring the pathogen an adulterant in some chicken products.
For most of us, balancing the desire to reduce sugar intake with our love of sweet foods and drinks is a constant battle.
There are myths, fads, and misconceptions associated with various aspects of our food supply, such as food additives and ingredients. Concerns and questions about sugars (caloric sweeteners) in foods have arisen.
Antioxidants—what are they and why do you need them? IFT Member Claudia Fajardo-Lira, PhD, Professor of Food Science and Nutrition at California State University-Northridge, explains the facts about antioxidants in this video.
Brief news items highlighting supplier news
This column describes how nutritional and overall wellness concerns evolve with age, and while some nutritional ingredients are important for all ages, the reason each age demographic seeks them out can vary.
A visually oriented overview of spice and seasoning ingredient trends.
With their sucrose-like functional properties, low caloric demand, consumer acceptability, and regulatory approval, rare sugars are poised to disrupt the sweetener market, say Cornell University researchers.
University of Florida researchers have identified compounds in citrus fruits that may have applications as natural sweeteners in food and beverage products.
In this podcast we’ll focus on some of nature’s herbs, spices and the extracts that offer potential health benefits. We'll also talk with the article's author, Linda Ohr, about what the research tells us, as well as some entrepreneurial companies who have tapped these spices' hidden potential for their current and future product innovation.