When vitamin C meets UV light curing material

When vitamin C meets UV photo-curing material
keywords
photo-curing heavy metal chelating vitamin C food safety
food safety is a permanent topic, as it involves everyone's health problems. And one of the topics of food safety is food packaging. For those involved in photo-curing applications, it should never be forgotten that nestle's 30 million-litre baby milk recall in Europe in 2005 caused by ITX
in
. How to provide safe and well-preserved packaging materials has always been an important part of continuous research and product development.
of heavy metal ions in food products is too high, it will not only harm the human body, but also lead to the loss of some nutrients in food. Vitamin C (i.e., L-astroviric acid) is a necessary nutrient of the human body, from the chemical structure it is an acidic polyhydroxy compound containing 6 carbon atoms, in the presence of oxidase and trace amounts of copper, iron and other heavy metal particles, will cause oxidation damage, loss of nutrition.
Figure 1 Molecular Structure of Vitamin C
Dr. Lin Zhuangsheng of Cornell University, USA, et al., using packaging materials prepared by photo-curing technology, can effectively absorb heavy metal ions, thereby greatly reducing their damage to vitamin C. Of course, there are many other health benefits for the control of heavy metal ions. Let's take a look at what Dr. Lin and others have done.
if traditional packaging materials need to be able to have co-operation with heavy metal particles, the most common method is to modifie the ontate of the material. This method is expensive, time-consuming, and affects other properties of the material. The coating of packaging materials using functional coatings is a very effective, convenient, cost-controllable, but also easy to scale up production and has a wide range of adaptable ways. However, since the coating of this functional coating is late, how to effectively combine the coating firmly with the coating substrate is a challenge in this way.
acetic acid (IDA) is very good for heavy metals and is often used for the removal of heavy metals. IDA also has good antioxidant effect and slows down the degradation of vitamin C. However, simply introducing the polar IDA unit, the resulting coating is easily swollen, becomes a material with hydrogel form, and is not suitable for food packaging materials need to release the packaged substances.
Andersen et al.' work, using emulsion co-polymerization, prepared polybutyl acrylates (GMA-IDA-
co
-BA-
co
-BPM) containing IDA erythropoietin groups and xybenzene erythropoietin groups. The polybutyl acrylates (BA) section here provides the thermal mechanical properties of the material while controlling the surface energy of the coating, while the diphenyl toluene group portion of 4-(methyl acrylamide)diphenyloxone (BPM) can be cross-linked with the polypropylene substrate in light conditions, allowing the coating to adhere securely to the base packaging material. The methyl acrylic shrinkage glyceride-gmathyl glyceric acid (GMA-IDA) unit obtained by the pre-acrylic and methyl acrylic shrinkage glycerides in the pre-eminante and methyl acrylic shrinkage glycerides (GMA-IDA) units provided for the cooperation of heavy metal chelates (Figure 2). And in this emulsion co-polymerization reaction, because GMA-IDA itself has the characteristics of both sexes, this emulsion polymerization can not add emulsifying agent.
Figure 2 Reaction schematics of triamgens of acrylic shrink glycerides-acetylene, orthobutyl acrylates and 4-(methyl acrylamide) xybenzene are obtained through emulsion co-polymerization
The preparation of the coating is to apply the emulsion of the above copolymer to the polypropylene film, to be evaporated by the solvent to obtain a clear glass-like polymer coating, and then use the power of 225mW/cm2 365nm ultraviolet light exposure for 180 seconds. After absorbing 365nm of photons, the xenon-based group of functions becomes a double free base three-line state that can extract hydrogen from the adjacent 3-H bond, forming two free-based. The two freelance fundamentals can be combined to form a cross-linking point (Figure 3), which allows the coating to adhere firmly to the polypropylene substrate. The coating after light curing is washed 3 times with 60oC deionized water for 30 minutes each to remove parts that are not connected to the substrate polymer. After this treatment, the roughness of the surface increases slightly.
figure 3 coating in light and polypropylene substrate cross-linking reaction
metal chelating coating treated with 20 sl/cm2 coating, with a chelating capacity of 1 iron ions at pH 3.0, pH 4.0 and pH 5.0, respectively 0.9±1.9nmol/cm2, 47.9±5.3nmol/cm2 and 156.0±13.8nmol/cm2, while unprocessed polypropylene materials use very little co-operation with metal ions. With the increase of pH, the stronger the coating is for the co-operation of the metal. The coating of 10μl/cm2 can be chelated to 19.8±5.2nmol/cm2 of
Fe
3 plus
, and when the coating is increased to 80μl/cm2, the chelating capacity of the
Fe
3 plus
can reach 134.3±7.7nmol/cm2. This means that the interior of the coating also produces co-chelation of iron ions, i.e. its chelation capacity to metal ions can be regulated by adjusting the thickness of the coating.
4 (A) is in a 0.06mM M iron chloride solution (pH 3.0-5.0) and is stored for 72 hours
Fe
3 plus
's chelating capacity; (B) under pH 4.0, different coating amounts of
Fe
3 plus
chelating capacity
transition metals can accelerate the oxidation and degradation of easily decomposed ingredients in packaged foods, vitamin C will be due to the presence of metal ions to accelerate its oxidation to dehydrogenated vitamin C. Dehydrogenated vitamin C is unstable and degrades further and loses its efficacy. The introduction of a metal chelating coating can greatly reduce the oxidation degradation of vitamin C and extend its degradation half-life to 20 days. It can also be seen from the experimental results of Figure 5 that samples using the external additive ethyl diethamilatic acid (EDTA) also have good antioxidant degradation in pH 3.0 conditions, but are far less than metal chelating coatings under pH 5.0 conditions.
Figure 5 uses a metal chelation coating (with a coating volume of 20 sl/cm2) to degrade vitamin C at pH 3.0 and pH 5.0
a metal chelation coating that is securely attached to the substrate by chemical bonds produced by photo-curing, and is also very stable under long-term contact with beverages or food. Experiments show that the coating does not fall off or break down in acidic, alcoholic, fatty or greasy environments.
of the reaction process of the preparation of the metal chelating polymer in Figure 6 (A) of the photo-cured metal, and (B) the reaction process diagram of the preparation of the metal chelating coatingThe work of Dr. Lin Zhuangsheng et al. introduces a polymer (
GMA-IDA-
co-
-BA-
co
-BPM
) that is first synthesized into a polymer that contains a co-chelation of metal particles, as well as photo-curable energy groups, and then securely adheres the coating to a polypropylene substrate, resulting in a packaging material with long-acting absorption of heavy metals. Effective absorption of heavy metals will greatly delay the loss of oxidation and decomposition of nutrients such as vitamin C, thus maintaining the active nutrients in the ingredients. Due to the presence of chemical bonding between the coating and the substrate, the coating is chemically and physically stable and does not peel or break down, even if exposed to grease, alcohol, acidic and watery packaging ingredients for a long time. This functional packaging material production method, simple and economical process, easy to enlarge production, for the upgrading of packaging materials has a good development prospects.