Dairy - Package Protection And Preservation

[Amazoniac]

This chapter of the book is so good that it deserved a thread for it:
Influence of light transmittance of packaging materials on the shelf-life of milk and dairy products — a review - Springer

 

[Amazoniac]

Patent US4253878 - Light protective bottle glass

Canadian beer is usually bottled in amber bottles, which greatly reduces the occurrence of so-called "skunky" or "light-struck" off-flavours in beer.

The usual containers for European beers sold in the United States are green. Accordingly, in order to compete against such beers, the usual containers for Canadian beers exported to the U.S. are green, non returnable bottles. Moreover, green bottles are demanded by certain breweries, because such bottles are usually clear, making it easy to determine whether the beer is clean.

It has been found that the use of green bottles for beer presents many problems with respect to the prevention of skunky off-flavours. Beer in green bottles is susceptible to light damage and display cabinets in the U.S. are often lighted by fluorescent tubes. The simple solutions of using amber bottles, totally enclosed six packs or high coverage labelling or wrapping are unacceptable to the distributor because he wishes to maintain the imported image of the green bottle.

 

[Amazoniac]

From the uploaded file (on transmittance):

@Dan Wich

 

[Dan W]

Interesting, I've been storing some liquids in brown glass, I was never sure how much it mattered.

I always thought healthnatura's post about plastic vs glass supplement bottling was interesting:

Light protection:
Amber glass is promoted as having superior light protection over plastic. While this is true for clear plastic it isn't true when compared to white LDPE plastic bottles. Amber glass has a very high clarity rate with an opacity of 10% and poor UV light filtering with a filter rate of 70%. Seventy percent sounds great doesn't it? But the UV filter rate is based on the opacity which is 10% or 70% of the 10%. This results in a actual UV protection rate of 7%.

Light Protection
White LDPE bottles have an opacity of 50% with a UV blocking rate of 99%. They block 99% of the 50% resulting in an actual protection rate of 48% compared to glass of 7%.

 

[Amazoniac]

Interesting, I've been storing some liquids in brown glass, I was never sure how much it mattered.

I always thought healthnatura's post about plastic vs glass supplement bottling was interesting:

Danzord, I suppose that they were mainly concerned with visible light.
The fluorescent lamps (shelf exposure) are coated to prevent UV transmittance, I don't how satisfactory they are. All glasses block UVb relatively fine. The vulnerable UV range depends on other factors such as thickness of the glass, its composition, its shape (most studies use a flat surface or only slightly curved). I read that in terms of changing thickness the impact is not so great, but you reduce 10-20% of transmittance here and there, and you end up with a great coverage as long as you avoid direct exposure.
Some questions then: how much of the UV rays from the sun can be reflected by materials, such as wall paints? How much is scattered through windows in shades? All this expecting that no one will leave their bottles exposed directly to the sun. And how much similar amber glass bottles can actually filter?

If something changes the properties of glass, making it alter its color and modify its ability to filter light, I don't understand why it wouldn't also affect the UV range, for the better or the worse.

Physics and Green Beer Bottles

 

[Amazoniac]

Patent EP2319811A1 - Protective beer bottle with high luminous transmittance
"Clearly, clear container glass offers almost no protection against ultraviolet and visible light. Green glass absorbs significant parts of the UV and visible light and amber glass - based on iron and sulphur - practically absorbs all radiation up to approximately 480 nm."
"Figure 1 clearly shows that below the cut-off wavelength of amber container glass, no significant amount of ultraviolet radiation and visible light can enter the content of an amber container glass."

Patent

 

[Amazoniac]

ESPN-13: 978-1-4398-6242-1

"The U.S. Pharmacopoeia (2004) defines a light-resistant container as one which passes no more than 10% of incident radiation at any wavelength between 290 and 450 nm through the average sidewall thickness. Amber glass provides this degree of light protection quite economically, as shown in Figure 8.2."

Out of curiosity:

"The addition of about 6% boron to form a borosilicate glass reduces the leaching of sodium (which is loosely combined with the silicon) from glass.
As a consequence of the sodium in glass being loosely combined in the silica matrix, the glass surface is subject to three forms of “corrosion”: etching, leaching and weathering. Etching is characterized by alkaline attack, which slowly destroys the silica network, releasing other glass components. Leaching is characterized by acid attack in which hydrogen ions exchange for alkali or other positively charged mobile ions. The remaining glass (principally silica) usually retains its normal integrity. Although not fully understood, weathering is not a problem in commercial glass packaging applications since it may take centuries to become apparent. However, a mild form of weathering is commonly known as surface bloom and may occur under extended storage conditions."

"Although glass has many of the properties of a solid, it is really a highly viscous liquid. During cooling, glass undergoes a reversible change in viscosity, the final viscosity being so high as to make the glass rigid for all practical purposes. Although glass at ambient temperatures has the characteristics of a solid, it is a supercooled liquid and will flow even at ambient temperatures over long periods of time, albeit extremely slowly."