Australian Health Today - - Contents -

Most foods de­grade and de­cay over time due to re­ac­tions with oxy­gen, de­com­po­si­tion of the food’s struc­ture or flavour com­pounds, or micro­organ­isms (or “mi­crobes”) caus­ing the food to spoil. The re­sult can be food that is ran­cid, smelly, slimy, has lost its colour or flavour, or is grow­ing things like mould.

We ap­ply our un­der­stand­ing of spoilage mech­a­nisms to ex­tend the shelf life of foods by slow­ing the rate of spoilage. We ex­clude oxy­gen by pack­ag­ing, slow re­ac­tion rates by re­frig­er­at­ing, gen­tly heat foods (blanch­ing, pas­teuri­sa­tion) to stop en­zymes and to kill mi­crobes. Nonethe­less, as con­sumers we want “fresher”, more nat­u­ral foods but many fresh and lightly pre­served foods will de­grade quickly.

Food qual­ity can de­te­ri­o­rate be­fore we per­ceive ob­vi­ous signs of spoilage. If al­lowed to grow to high lev­els, some mi­crobes that may con­tam­i­nate foods (col­lec­tively called “pathogens”) can cause food­borne ill­ness, or “food poi­son­ing”. Of­ten th­ese mi­crobes don’t vis­i­bly spoil the food so we can’t tell if a food has be­come un­safe.

To pro­tect con­sumers against poor qual­ity or po­ten­tially haz­ardous foods, gov­ern­ments have in­tro­duced “date codes” to help con­sumers eval­u­ate the “fresh­ness” of foods. Food pro­duc­ers also em­brace date codes to help them pro­vide safe, high qual­ity prod­ucts to con­sumers.

Do we re­ally have to pay at­ten­tion to ‘use-by’ and ‘best-be­fore’ dates?

In Aus­tralia and New Zealand, we spec­ify “use-by” and “best-be­fore” dates for per­ish­able and semiper­ish­able foods that are ready-to-eat with­out cook­ing. Food ex­pected to re­main whole­some for more than two years, in un­opened pack­ages, don’t re­quire th­ese la­bels and there are other types of date codes for bread.

Sim­i­lar reg­u­la­tions op­er­ate in Euro­pean Union coun­tries, but the United States and other na­tions have a plethora of food date codes that don’t read­ily cor­re­spond with our “use-by” and “best-be­fore” dates. In gen­eral, there is lit­tle har­mon­i­sa­tion in­ter­na­tion­ally for food date codes which has been iden­ti­fied as a bar­rier to trade. Per­haps un­sur­pris­ingly, sur­veys in the United King­dom and US showed that many con­sumers don’t un­der­stand the mean­ing of var­i­ous date codes on foods.


A “use-by” date is re­quired for foods that might, over time, sup­port the growth of cer­tain pathogens un­der the spec­i­fied stor­age con­di­tions. A “use-by” date, then, re­lates to food safety and in­di­cates the time when the food may be­come less safe to eat.

Foods can­not legally be sold, and should not be con­sumed, be­yond their “use-by” dates and should be dis­carded. “Use-by” dates are also re­quired on spe­cially for­mu­lated foods for med­i­cal pur­poses given, for ex­am­ple, to peo­ple with in­her­ited meta­bolic dis­or­ders whose di­etary needs can­not be met by a nor­mal diet.

For th­ese foods, the “use-by” date in­di­cates when essen­tial nu­tri­ents in the food will have de­graded to lev­els so low that the food no longer pro­vides the in­tended ther­a­peu­tic ben­e­fit.

Best Be­fore

A “best-be­fore” date pro­vides ad­vice about the ex­pected qual­ity of the prod­uct and is the time be­yond which, in the food man­u­fac­turer’s opin­ion, the prod­uct will no longer be in op­ti­mal con­di­tion. It will, how­ever, prob­a­bly still be ed­i­ble and nu­tri­tious for some time af­ter that date.

Food pro­duc­ers usu­ally ap­ply con­ser­va­tive “best­be­fore” dates to en­sure that con­sumers have enough time af­ter pur­chase to use the food in good con­di­tion. Con­sumers can ex­er­cise judge­ment about foods be­yond their “best-be­fore” date: if it looks OK, and smells OK, it’s prob­a­bly OK to eat, though not at its best.

This ap­proach must not be used for foods be­yond their “use-by” date, since pathogens can be present with­out af­fect­ing the sen­sory qual­i­ties of the food.

Waste not, want not

Ac­cu­rately spec­i­fy­ing “useby” and “best-be­fore” dates is chal­leng­ing, re­quir­ing ex­ten­sive sci­en­tific tri­als and/or knowl­edge be­cause of the range of foods, spoilage pro­cesses and food preser­va­tion tech­nolo­gies. Ex­pert guid­ance is avail­able to food pro­duc­ers from a num­ber of sources. Some­times, how­ever, there’s un­cer­tainty about whether a “use-by” or “shelf life” date should be ap­plied if its not known whether pathogens are re­al­is­ti­cally likely to be present, and able to grow, in the par­tic­u­lar type of food or not.

Our ca­pac­ity to pro­duce enough food for Earth’s pop­u­la­tion is be­com­ing a real con­cern, yet 20-30% of the world’s food is wasted. A con­se­quence of con­fu­sion about the cor­rect spec­i­fi­ca­tion of “best­be­fore” and “use-by” dates is that some foods are un­nec­es­sar­ily dis­carded even though they are safe to eat and nu­tri­tious.

De­vel­op­ing ap­pro­pri­ate “use-by” and “best­be­fore” dates could help re­duce this wastage. Help­ing con­sumers to min­imise their wastage of food through un­der­stand­ing of “best-be­fore” dates of­fers an­other small, but po­ten­tially use­ful, con­tri­bu­tion to global food se­cu­rity.

As an ad­di­tional tip to re­duce wastage, if foods are un­likely to be con­sumed be­fore the “use-by” or “best-be­fore” date, they can be frozen (which es­sen­tially stops spoilage pro­cesses) and thawed for con­sump­tion later, pro­vided they’re eaten soon af­ter thaw­ing.

de­vel­op­ing ap­pro­pri­ate “use-by” & “best-be­fore” dates could help re­duce

this wastage.

Writ­ten by Dr. Tom Ross, As­so­ciate Pro­fes­sor in Food Mi­cro­bi­ol­ogy, uni­ver­sity of Tas­ma­nia and co-au­thored by

Dr. Wayne An­der­son, Di­rec­tor Food sci­ence and stan­dards Divi­sion, Food Safety Au­thor­ity of Ire­land. Ar­ti­cle first ap­peared on­line at www.the­con­ver­sa­

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