C
onsumers rely on expiration dates to
judge whether a perishable good has gone
bad. However, the date calculation is often
difficult to estimate and sometimes inaccurate,
as the package may go through unpredictable
cond i t i ons th roughout the manufactu r i ng
and deliver y processes. Hence, opening an
“unexpired” milk carton only to be greeted with
sour or discoloured milk is a situation familiar to
many. Wouldn’t it be helpful if an indicator could
tell us the level of freshness before we even open
the package to avoid the smell, or worse, food
poisoning?
Other than contamination, there are two
main reasons for the spoilage of food: bacterial
growth and biochemical degradation. These
two factors are highly dependent on the storage
temperature: at warm temperatures, bacteria
multiply faster, and chemical degradation also
occurs more rapidly. Therefore, we can attempt
to resolve the problem if we can create an
indicator that simulates the rates of these two
reactions, and attach it to the packaging during
manufacture so that it experiences the same
temperature variations as the food.
Engineering the tag is easier said than done.
How do we programme the indicator to mirror
the specific food inside the package? How do
we make it easy for the consumer to understand
the indicator? Perhaps most importantly, how do
we make the indicator affordable for large-scale
commercial use?
T
ags
For Food Freshness
食物變質智能標簽
S
mart
By Raphaella So
蘇韋霖
Oxidation-reduction
, or “REDOX,” is a type of chemical
reaction involving the transfer of electrons from one element to
another. Ascorbic acid is a potent electron-donor (also called
“reducing agent” because the negative charge of electrons
“reduces” the target), so it can react with positively charged
silver ions to form neutral silver metal.
氧化還原
（英文
oxidation-reduction
）是個轉移電子的化學反應。抗壞
血酸是個很強的復原劑，它可以把自己的電子送出去把對象的氧化數降
低。因此，抗壞血酸可以和正氧化數的銀離子產生化學反應，製造中性氧
化數的銀金屬。
References
[1] Zhang C. et al.
Time-Temperature Indicator for Perishable Products Based on Kinetically Programmable Ag Overgrowth on Au Nanorods
.
Retrieved from
This article may be useful for classes learning about “Redox Reactions”
based on the DSE Chemistry syllabus.
根據
DSE
化學科目，這篇文章有助學習關於「氧化還原」的課程。
