Question

Which of the following is main function of lug-type or twist cap?

(a) Closures to retain internal pressure

(b) Closures to contain and protect contents

(c) Closures to maintain vacuum inside container

(d) Closures to secure contents inside containe

I had been asked this question during an interview.

My enquiry is from Glass as Packaging Material topic in portion Glass Packaging Materials of Food Packaging Technology

Answer 1

The correct choice is (c) Closures to maintain vacuum inside container

To elaborate: Closures used with food containers can be classified under four chidings. They are-

i. Closures to retain internal pressure – They retain an internal pressure of 200-800 kPa, as found in carbonated drinks and beer. Ex. Crown cork, Roll-on tamper evident aluminum closure

ii. Closures to contain and protect contents – They contain and protect the contents with no internal pressure (Ex. Wine in a bottle). Ex. Bark cork

iii. Closures to maintain vacuum inside container – They maintain a vacuum inside glass containers that typically contain heat-processed food. Ex. Lug-type or twist cap, Press-on twist –off cap, Pry-off (side seal) cap

iv. Closures to secure contents inside container – They are to secure the contents inside the glass container (Ex. Peanut butter).