Respiratory and low-temperature sweetening responses of fresh-cut potato (Solanum tuberosum L.) tubers to low oxygen

Enzymatic browning (EB) has impeded the commercialization of fresh-cut (FC) potato. However, recently introduced Innate (R)-engineered cultivars with silenced polyphenol oxidase (PPO) have overcome this obstacle. As a supplement to refrigeration, low O-2 atmosphere may extend the shelf-life of FC potato by reducing wound-induced respiration, associated dry matter loss, EB, and low-temperature sweetening (LTS). Determining the O-2 concentration that minimizes these deteriorative physiological processes without invoking anaerobic metabolism is prerequisite to designing effective modified atmosphere packaging (MAP). Accordingly, FC tubers of cultivars Russet Burbank (RB), Ranger Russet (RR), and their Innate (R) counterparts, CultivATE (R) , GenerATE (R) , and GlaciATE (R) , were stored (4 degrees C) in ten O-2 atmospheres ranging from 0 to 21 kPa to determine the lower oxygen limit (LOL) for aerobic respiration and effects on LTS and EB. FC tissue stored at 21 kPa O-2 displayed a prominent cold-induced respiratory acclimation response (RAR), characterized by an initial decline in respiration rate followed by a steady increase through 48 h. The RAR decreased with O-2 and was extinguished at <= 1.5 kPa. Lowering O-2 from 21-7 kPa had little effect on tissue respiration; however, rates fell from 4.23 to 3.41 mu g kg(-1) s(-1) as O-2 decreased from 7 to 3.5 kPa, followed by a further 79% reduction to 0.70 mu g kg(-1) s(-1) at 0 kPa O-2. Tissue lactate profiles revealed the onset of anaerobic metabolism at ca 1.5 kPa O-2 for all cultivars. Importantly, lactate and ethanol accumulation were negligible through 16 d at >= 2 kPa O-2 (= LOL) but increased considerably at <= 1 kPa. Low O(2 )attenuated the cold-induced synthesis of sucrose and reducing sugars in FC tissue from RB, and sucrose from GlaciATE (R) tubers in which acid invertase is silenced. Enzymatic browning of FC RB and RR tubers was inhibited by anoxia, but extensive at >= 0.5 kPa O-2. FC Innate (R) tubers exhibited only minor EB at all O-2 concentrations. Collectively, these data inform the further development of MAP for FC potato.