Heat during processing of the fresh juices (barley grass juice in this case) can cause the most damage, especially when moisture content is high. As the juice turns into powder, however, it is less susceptible to damage and deactivation of the enzymes by heat. After the powder is fully dried, it can withstand heat much more effectively.
The powder is somewhat like a dormant seed. While the seed is kept dry, it is very stable at elevated temperatures. Place it in a moist and warm environment and it will sprout with new life. The powder of properly dehydrated juice powder is very stable at warm temperatures but, when reconstituted in water, it is enzymatically alive and will not tolerate excessive heat without degradation.
The 110 – 120°F temperatures in the back of the UPS or USPS truck are not too extreme for the fully dried powder. Damage is minimal as long as the jars remain sealed, preventing moisture from compounding the high heat conditions.
Our testing of old expired BarleyMax powder showed that it was still more enzymatically active than many other similar, non-expired powders on the market, showing the stability of the BarleyMax powder. (Either high heat for a short time or lower heat for a long time would have similar effects on the powder, so that is a pretty good test.) The powders tested in our lab are shipped to the lab by standard shipping.