Fabrication and design of poly(l‐lactic acid) membrane for passive MAP packaging of Brassica chinensis L

Abstract

PLDxL copolymers were synthesized from physically stable rigid poly(l‐lactic acid) (PLLA) and a few different molecular weights of polydimethylsiloxane (PDMS) to increase the O2 and CO2 permeabilities of PLLA films and make them acceptable for packaging highly respirable products. The effect of PDMS on the morphology, mechanical properties, and gas permeability of PLDxL was investigated. Copolymers showed approximately 10 times the fracture strain and 1.7 times the CO2 and O2 permeabilities of neat PLLA. Additionally, PLDxL maintained an increased CO2/O2 perm‐selectivity consistent between 5 and 40°C. Passive modified atmosphere packaging of Brassica chinensis L was developed to assess the membrane's impact on headspace gas inside the package. The results showed that poly(amide)/poly(ethylene) packaging with 48 cm2 PLD1.8L membrane as a breathing window can provide 50 g B. chinensis L. with a healthy atmosphere of 3%–8% O2 and 5%–8% CO2 between 6 and 22 days. Vegetables packaged in PLD1.8L had the lower respiration rate, lower nitrite contents, and less proliferation of microorganisms. Moreover, a suitable atmosphere kept vegetables with higher ascorbic acid and a good appearance after more than 2 weeks of storage at 5°C. Practical Application The permeability of the PLLA‐based membrane can be adjusted for the breathable window membrane of sealed fresh products. In the future, several types of film could be developed to match the respiratory and metabolic characteristics of different kinds of products. Such PLLA‐based specialized membranes can refine the fresh‐keeping function and be more attractive to the customer.

Progress in the Preparation and Application of Breathable Membranes

“…Conversely, too low oxygen levels result in the accumulation of anaerobic metabolites, such as ethanol, which negatively affects the storage of freshly picked fruits and vegetables [ 117 ]. Therefore, microporous and breathable packaging materials can be used to regulate the gas transfer rate (GTR), which means maintaining the optimal equilibrium concentration of oxygen (O 2 ) and carbon dioxide (CO 2 ) inside food packaging to solve this problem [ 118 , 119 ]. Additionally, these materials help prevent the intrusion of insects and microorganisms and block water infiltration, thereby preserving the freshness and quality of the food products [ 17 , 120 ].…”