Our focus on corks, and just corks, is the foundation on which Portocork has been built. Since our inception, we’ve produced more than 6 billion natural corks. So how do we do what we do, and maintain the highest level of quality?  Here’s our story

Test, Test and Test more…

We were founded in 1982 by Portocork International and Fleming Packaging Group of Napa and fully acquired by Portocork International in 1996. Portocork International is headquartered in Santa Maria de Lamas, Portugal with modern production facilities that process natural cork sourced only from company-managed forests in Portugal.

Our Lab

Thus, Portocork controls the cork from the time it is harvested until it arrives as finished product at the winery. Our cork undergoes rigorous testing in their ISO-9002 certified Portuguese facilities (on raw material and after becoming a stopper) and again in our Napa laboratory, ensuring that Portocork closures are the highest quality year after year. An example of Portocork International’s industry leadership is their screening for TCA. Every single bale of 10,000 cork is tested for TCA using GC/MS before the washing process, greatly reducing the risk of cross contamination. This preliminary testing is unique among cork producers. Following the wash, Portocork conducts additional TCA testing on bales prior to their shipment to the U.S. This extra effort has resulted in reductions of more than 96% in the TCA levels of incoming cork to our Napa facility since 2001.


Once the cork arrives at our Napa facility, it undergoes comprehensive testing by Portocork’s team of scientists led by Dr. Isabelle Sodini in our in-house laboratory. Dr. Sodini and her staff put incoming cork through chemical, sensory and visual testing to ensure each bale meets Portocork’s highest quality standards. We use Cork Quality Council (CQC) methodologies as our basis for TCA testing but exceed the Council’s criteria by sampling more than double the amount of required corks. All required chemical testing is sent out to a 3rd party lab for independent validation.  And where many U.S. suppliers have foregone sensory testing, Portocork has broadened our sensory testing as it has proven to detect other off flavors that go unnoticed in chemical testing.  Portocork’s analytical capabilities include our own in-house GC/MS which allows us to test a lot more than is required by the CQC or assist our winery clients tailor-made QC protocols.  In 2016 more than 3,000 TCA tests were run on our own Gas Chromatography equipment.


Approved corks move from our lab into production where they are printed and coated. Once coated, corks go into Portocork’s humidification chamber for 24-48 hours to raise the moisture content to 5.5-7.5%. Our state-of-the-art humidifier is unique in that it also releases Ozone into the cork for 2 hours per day to ensure sterility. After the Portocork lab verifies moisture content, corks enter our surface treatment area where electronically-controlled equipment is specially calibrated to apply the precise amount of coating needed for consistent ease of cork insertion and extraction. Finished corks are counted and moved to our final inspection tables where skilled technicians inspect every single cork. Corks are moved around our facility by gravity-based equipment that we invested in to prevent the mixing and chipping commonly found in forcibly-blown corks. Before an order can be shipped to a client, the order must pass our stringent Quality Assurance tests on the final product to ensure the product meets specification (moisture, extraction, So2 level injection).