Refrigeration and food safety

Long time no post! I’ve lapsed again but now I’m back. I thought I’d re-start with a post I’ve been ruminating about for some time: refrigeration and food safety.

There have been various periods in my life during which I have been guilty of having a refrigerator full of moldy, expired items due to complete neglect. Generally speaking, putting leftovers in the fridge more often than not results in certain leftover death. As I’ve been cooking more, however, I’ve been getting better at storing foods and cleaning out the refrigerator. I have encountered a few articles about food safety recently so I thought I’d share some newfound knowledge. Some of this is certainly confirmatory of what you already know, but some might surprise you. I’ve extracted mostly verbatim from six sources (see below), cutting and pasting the interesting portions together into a complete and organized guide. See below for sources. Please let me know what I missed or feel free to add to this in your comments. Look forward to hearing from you!

Types of Bacteria in Refrigerated Foods

There are two completely different families of bacteria: pathogenic bacteria, the kind that cause foodborne illness, and spoilage bacteria, the kind of bacteria that cause foods to deteriorate and develop unpleasant odors, tastes, and textures. Pathogenic bacteria can grow rapidly in the "Danger Zone," the temperature range between 40 and 140 °F, but they do not generally affect the taste, smell, or appearance of a food. In other words, one cannot tell that a pathogen is present. On the other hand, spoilage bacteria can grow at low temperatures, such as in the refrigerator. Eventually they cause food to develop off or bad tastes and smells. Most people would not choose to eat spoiled food, but if they did, they probably would not get sick. It comes down to an issue of quality versus safety:

• Food that has been left too long on the counter may be dangerous to eat, but could look fine.
• Food that has been stored too long in the refrigerator or freezer may be of lessened quality, but most likely would not make anyone sick. (However, some bacteria such as Listeria monocytogenes thrive at cold temperatures, and if present, will multiply in the refrigerator and could cause illness.)

Starting Off on the Right Foot: Understanding Expiration Dates

Most packaged foods include some type of expiration, sell-by or use-by date imprinted on the container. Figuring out the intent of that date is not always an easy matter. Even the general industry terms for it, open-dating and closed dating, raise questions.

Surprisingly, dating is not required by US federal law, with the exception of infant formula and baby foods which must be withdrawn by their expiration date. For all other foods, except dairy products in some states, freshness dating is strictly voluntary on the part of manufacturers. To further shake your confidence, stores are not legally required to remove outdated products from their shelves. So, it's the old caveat even when it comes to food: Buyer beware and always read the label.

Expiration date terminology

These terms all apply to unopened products. Once opened, refer to food storage chart below to understand how long foods can be kept.

Best if used by and use-by date: With emphasis on the best qualifier in this term, it means the product should retain maximum freshness, flavor and texture if used by this date. It is not a purchase-by or safety date. Beyond this date, the product begins to deteriorate, although it may still be edible.

Expiration date: If you haven't used the product by this date, toss it out. Other dating terms are used as a basic guideline, but this one means what it says.

Sell-by or pull-by date: This date is used by manufacturers to tell grocers when to remove their product from the shelves, but there is generally still some leeway for home usage. For example, milk often has a sell-by date, but the milk will usually still be good for at least a week beyond that date if properly refrigerated.

Guaranteed fresh: This date is often used for perishable baked goods. Beyond this date, freshness is no longer guaranteed although it may still be edible.

Pack date: This is the date the item was packed, most-used on canned and boxed goods. It is usually in the form of an encrypted code not easy to decipher. It may be coded by month (M), day (D), and year (Y), such as YYMMDD or MMDDYY. Or it may be coded using Julian (JJJ) numbers, where January 1 would be 001 and December 31 would be 365. In even more convoluted coding, letters A through M (omitting the letter I) are often assigned to the months, with A being January and M being December, plus a numeric day, either preceded or followed by the numeric year.

Keeping Opened Food Safe: Safe Refrigerator and Freezer Temperatures

Refrigerators should be set to maintain a temperature of 40 °F or below. An appliance thermometer can be kept in the refrigerator to monitor the temperature. This can be critical in the event of a power outage. When the power goes back on, if the refrigerator is still 40 °F, the food is safe. Foods held at temperatures above 40 °F for more than 2 hours should not be consumed. Appliance thermometers are specifically designed to provide accuracy at cold temperatures. Be sure refrigerator/freezer doors are closed tightly at all times. Don't open refrigerator/freezer doors more often than necessary and close them as soon as possible.

Don’t keep the refrigerator too cool! As you approach 32 °F, ice crystals can begin to form and lower the quality of foods such as raw fruits, vegetables and eggs.

The freezer temperature should be 0°F or below.

How to Avoid Illness and Spoilage? Refrigerate Promptly and Properly

• Refrigerate foods quickly because cold temperatures slow the growth of harmful bacteria. Do not over-stuff the refrigerator. Cold air must circulate to help keep food safe. Keeping a constant refrigerator temperature of 40°F or below is one of the most effective ways to reduce the risk of foodborne illness.
  Refrigerate or freeze meat, poultry, eggs and other perishables as soon as you get them home from the store.
• Never let raw meat, poultry, eggs, cooked food or cut fresh fruits or vegetables sit at room temperature more than two hours before putting them in the refrigerator or freezer (one hour when the temperature is above 90°F).
• Hot food can be placed directly in the refrigerator or it can be rapidly chilled in an ice or cold water bath before refrigerating. Cover foods to retain moisture and prevent them from picking up odors from other foods. Always marinate food in the refrigerator.
• Divide large amounts of leftovers like soup into shallow containers for quicker cooling in the refrigerator. A large cut of meat or whole poultry should be divided into smaller pieces and wrapped separately or placed in shallow containers before refrigerating
• Use or discard refrigerated food on a regular basis.

Proper Defrosting

Never defrost food at room temperature. Food must be kept at a safe temperature during thawing. There are three safe ways to defrost food: in the refrigerator, in cold water, and in the microwave. Food thawed in cold water or in the microwave should be cooked immediately. Never defrost food in hot water.

It is safe to freeze previously cooked or uncooked foods that have thawed properly, although there may be a loss of quality because of moisture lost through defrosting.

Don’t Keep Food for Too Long: Storage Times For Refrigerated Foods and Frozen Foods

As a random side-note, it is not necessarily safe to cut bits of mold off cheese and eat the seemingly unaffected portion because spoilage (and sometimes toxins) could go beyond the visible mold. The U.S. Department of Agriculture says that if you cut off at least 1 inch around and below the mold spot, hard cheeses can still be safely consumed. Intentional mold, such as that found on Stilton, is safe because it has purposely been introduced during the cheese-making process and is “good” mold). Also (not noted in the chart linked below): ground spices can be kept for two or three years; whole spices for three or four years; herbs for one to three years. Store spices and herbs tightly sealed in a cool, dry place. Red spices retain their color better and are best protected from insects if refrigerated.

Product	Refrigerator (40 °F)	Freezer (0 °F)
Eggs
Fresh, in shell	3 to 5 weeks	Don't freeze
Raw yolks, whites	2 to 4 days	1 year
Hardcooked	1 week	Don't freeze well
Liquid pasteurized eggs, egg substitutes, opened unopened	3 days 10 days	Don't freeze well 1 year
Mayonnaise
commercial refrigerate after opening	2 months	Doesn't freeze
Deli & Vacuum-Packed Products
Store-prepared (or homemade) egg, chicken, ham, tuna, macaroni salads	3 to 5 days	Doesn't freeze well
Hot dogs & Luncheon Meats
Hot dogs, opened package unopened package	1 week 2 weeks	1 to 2 months 1 to 2 months
Luncheon meats, opened package unopened package	3 to 5 days 2 weeks	1 to 2 months 1 to 2 months
Bacon & Sausage
Bacon	7 days	1 month
Sausage, raw from chicken, turkey, pork, beef	1 to 2 days	1 to 2 months
Smoked breakfast links, patties	7 days	1 to 2 months
Hard sausage--pepperoni, jerky sticks	2 to 3 weeks	1 to 2 months
Summer sausage--labeled "Keep Refrigerated" opened unopened	3 weeks 3 months	1 to 2 months 1 to 2 months
Ham, Corned Beef
Corned beef, in pouch with pickling juices	5 to 7 days	Drained, 1 month
Ham, canned--labeled "Keep Refrigerated" opened unopened	3 to 5 days 6 to 9 months	1 to 2 months Doesn't freeze
Ham, fully cooked vacuum sealed at plant, undated, unopened	2 weeks	1 to 2 months
Ham, fully cooked vacuum sealed at plant, dated, unopened	"use by" date on package	1 to 2 months
Ham, fully cooked, whole	7 days	1 to 2 months
Ham, fully cooked, half	3 to 5 days	1 to 2 months
Ham, fully cooked, slices	3 to 4 days	1 to 2 months
Hamburger, Ground & Stew Meat
Hamburger & stew meat	1 to 2 days	3 to 4 months
Ground turkey, veal, pork, lamb & mixtures of them	1 to 2 days	3 to 4 months
Fresh Beef, Veal, Lamb, Pork
Steaks	3 to 5 days	6 to 12 months
Chops	3 to 5 days	4 to 6 months
Roasts	3 to 5 days	4 to 12 months
Variety meats--tongue, liver, heart, kidneys, chitterlings	1 to 2 days	3 to 4 months
Pre-stuffed, uncooked pork chops, lamb chops, or chicken breast stuffed with dressing	1 day	Don't freeze well
Soup & Stews
Vegetable or meat added	3 to 4 days	2 to 3 months
Meat Leftovers
Cooked meat and meat casseroles	3 to 4 days	2 to 3 months
Gravy and meat broth	1 to 2 days	2 to 3 months
Fresh Poultry
Chicken or turkey, whole	1 to 2 days	1 year
Chicken or turkey, pieces	1 to 2 days	9 months
Giblets	1 to 2 days	3 to 4 months
Cooked Poultry
Fried chicken	3 to 4 days	4 months
Cooked poultry casseroles	3 to 4 days	4 to 6 months
Pieces, plain	3 to 4 days	4 months
Pieces covered with broth, gravy	1 to 2 days	6 months
Chicken nuggets, patties	1 to 2 days	1 to 3 months
Pizza
Pizza	3 to 4 days	1 to 2 months
Stuffing
Stuffing—cooked	3 to 4 days	1 month
Beverages, Fruit
Juices in cartons, fruit drinks, punch	3 weeks unopened 7 to 10 days opened	8 to 12 months
Dairy
Butter	1 to 3 months	6 to 9 months
Buttermilk	7 to 14 days	3 months
Cheese, Hard (such as Cheddar, Swiss)	6 months, unopened 3 to 4 weeks, opened	6 months
Cheese Soft (such as Brie, Bel Paese)	1 week	6 months
Cottage Cheese, Ricotta	1 week	Doesn't freeze well
Cream Cheese	2 weeks	Doesn't freeze well
Cream--Whipped, ultrapasteurized	1 month	Doesn't freeze
Cream--Whipped, Sweetened	1 day	1 to 2 months
Cream--Aerosol can, real whipped cream	3 to 4 weeks	Doesn't freeze
Cream--Aerosol can, non dairy topping	3 months	Doesn't freeze
Cream, Half and Half	3 to 4 days	4 months
Eggnog, commercial	3 to 5 days	6 months
Margarine	4 to 5 months	12 months
Milk	7 days	3 months
Pudding	package date; 2 days after opening	Doesn't freeze
Sour cream	7 to 21 days	Doesn't freeze
Yogurt	7 to 14 days	1 to 2 months
Dough
Tube cans of rolls, biscuits, pizza dough, etc.	Use-by-date	Don't freeze
Ready-to-bake pie crust	Use-by-date	2 months
Cookie dough	Use-by-date unopened or opened	2 months
Fish
Lean fish (cod, flounder, haddock, sole, etc.)	1 to 2 days	6 months
Fatty fish (bluefish, mackerel, salmon, etc.)	1 to 2 days	2 to 3 months
Cooked fish	3 to 4 days	4 to 6 months
Smoked fish	14 days or date on vacuum package	2 months in vacuum package
Shellfish
Shrimp, scallops, crayfish, squid, shucked clams, mussels and oysters	1 to 2 days	3 to 6 months
Live clams, mussels, crab, lobster and oysters	2 to 3 days	2 to 3 months
Cooked shellfish	3 to 4 days	3 months

Note: These short but safe time limits will help keep refrigerated foods
from spoiling or becoming dangerous to eat. Because freezing keeps food safe
indefinitely, recommended storage times are for quality only. Storage times are
from date of purchase unless specified on chart. It is not important if a date
expires after food is frozen.

Can Food be Stored Safely Anywhere in the Refrigerator?

According to Cooks Illustrated, refrigerator temperature can vary greatly over the course of the day and within the various compartments and areas of the refrigerator. The middle shelf on the door and the front portion of the bottom cabinet shelf are the warmest areas – ranging up to 43 degrees. The meat compartment is the coolest area of the refrigerator (on average 33 degrees). Place refrigerator thermometers in the top, middle and bottom shelves of your refrigerator, recording the temperature every couple of hours if you want to understand the variations in your own refrigerator’s temperature (or just trust Cooks Illustrated’s advice below...)

Some fruits and vegetables are particularly sensitive to chill (including berries, citrus fruits, melons, corn on the cob and snap beans) and should not be stored below 37 degrees Fahrenheit. Other chill-injury prone fruits and vegetables should not be refrigerated at all. These include tropical fruits (mangoes, pineapples – may be refrigerated up to two days when fully ripe), avocados, tomatoes, bananas and pickling cucumbers – who knew?

For optimal storage results, here’s where unfailingly precise pros at Cook’s Illustrated recommend storing your food:

Door, butter compartment (temperature: moderate)

• Herbs

Door, middle compartment (temperature: warm)

• Condiments

Door, bottom compartment (temperature: cool)

• Milk (gallon-sized containers may be stored on the back portion of the top shelf)
• Sour cream
• Yogurt

Top shelf, front (temperature: moderate)

• Eggs in the carton (note: do not store eggs on the door contrary to popular opinion: the door is too warm)
  Butter in a butter dish

Top shelf, back (temperature: cool)

• Refrigerator-safe fruits, such as apples and grapes
• Lunch meats stored in zipper-lock bags

Middle shelf, front (temperature: moderate)

• Chill-sensitive fruits and vegetables such as melons and beans (green beans, wax beans)

Middle shelf, back (temperature: cool)

• Prepared foods and leftovers

Bottom shelf, front (temperature: warm)

• Chill sensitive fruits and vegetables such as subtropical fruits, mushrooms (stored in original packaging or a zipper-lock bag, with air holes), and corn (wrapped in a wet paper bag and placed in a plastic bag)

Bottom shelf, back (temperature: cool)

• Whole birds, roasts wrapped in original wrapper or placed in plastic bags
• Fish and shellfish, placed on top of zipper-lock bags of ice inside a deep plastic container

Meat compartment (temperature: cool)

• Ground meat
• Chops
• Cutlets
• Steaks
• Chicken parts

Crisper (temperature: moderate to cool)

• Leafy greens (completely dried) in a plastic container or salad spinner
• Celery
• Asparagus
• Broccoli
• Cheese (wrapped in parchment paper and then foil)

Sources:

• USDA, Food Safety and Inspection Service
• The Food Keeper, The Food Marketing Institute
  Partnership for Food Safety Education (www.fightbac.org)
• About (http://about.com/)
• Consumer Reports: Is that Safe to Eat? (December, 2006)
• Cook’s Illustrated: Getting to Know Your Refrigerator

(note: I’ve extracted mostly verbatim from the above six sources, cutting and pasting the interesting portions together into a complete and organized guide)