Packaging, Storage, and Shelf-Life
This domain tests how package materials and storage conditions control moisture, oxygen, light, and microbial growth, and how shelf life is established. Expect questions on barrier properties, modified atmosphere, active packaging, and accelerated shelf-life testing.
Core rules
- Barrier performance is described by oxygen transmission rate and water vapor transmission rate. Metallized films, EVOH, and foil provide high oxygen barrier; polyethylene provides moisture barrier but poor oxygen barrier. Grease resistance and light protection matter for sensitive products.
- Vacuum packaging removes oxygen and relies on low-oxygen conditions; anaerobic and facultative organisms remain a risk. Modified atmosphere packaging adjusts carbon dioxide, nitrogen, and oxygen. Carbon dioxide inhibits many bacteria and molds but dissolves into product water, causing package collapse. Nitrogen is an inert filler. High oxygen maintains red meat color through oxymyoglobin.
- Active packaging includes oxygen scavengers, ethylene absorbers, moisture regulators, and antimicrobial films. Aseptic packaging allows shelf-stable UHT products. Migration from packaging into food must be within regulatory limits.
- Shelf-life testing may be real-time or accelerated. The Q10 concept states that reaction rate multiplies for each 10°C rise. Date labeling depends on product type and jurisdiction.
Worked example
A chilled ready meal has a 10-day shelf life at 20°C. With Q10 = 2, storage at 30°C doubles the reaction rate, so the predicted life is approximately 5 days. If an accelerated test at 30°C shows spoilage at 5 days, the estimate at 20°C is about 10 days, provided the spoilage mechanism does not change. If the product is MAP-packed, the package headspace and gas-to-product ratio must match commercial conditions.
Traps that cost marks
Treating MAP as a sterilization step. Expecting an oxygen scavenger in a package of respiring produce. Ignoring that carbon dioxide dissolution can collapse a package. Using Q10 predictions when the failure mechanism changes with temperature.