Light levels below the light compensation point prolong the shelf life of fresh-cut butterhead lettuce

Compared to dark storage, application of 5 ?mol m-2 s-1 PAR, a light level below the light compensation point, prolonged the shelf life of fresh-cut lettuce by 50 to 100%. The increase in tissue electrolyte level, an indicator of loss of membrane integrity, was greatly delayed in the lit samples. Dark storage caused a rapid depletion of chlorophyll, carotenoids, ascorbic acid and carbohydrates. In the lit samples, chlorophyll and carotenoids decreased similarly to the dark stored samples but ascorbic acid and carbohydrates (glucose, fructose, sucrose and starch) showed a marked increase. In lit samples total carbohydrates increased to approximately 20 mg g-1 FW; over 10 times the original levels and the levels in dark stored samples. Measurements of photosynthetic activity confirmed that there was no net photosynthesis in the lit samples during the storage period. The accumulation of sugar and ascorbic acid and the prolonged shelf life were not much influenced by the spectral properties of the light source. Similar results were obtained both under low levels of white light from fluorescent tubes and under monochromatic red, blue and green light provided by LEDs. The prolonged shelf life of low light-treated samples is possibly due to the higher levels of sugar and ascorbic acid that may act as antioxidants, may preserve membrane integrity and may provide sufficient respiratory substrate to prevent ATP depletion. We hypothesize that, under low light conditions, sugars may be produced through the processing of chloroplast degradation products in the glyoxysome,subsequent production of malate and oxaloacetate and production of glucose through reversal of the glycolysis pathway(gluconeogenesis). The role of low light in triggering this alternative sugar generation mechanism is discussed. ? Original title, authors, and sources Light levels below the light compensation point stimulate an alternative sugar generation mechanism and prolong the shelf life of fresh-cut butterhead lettuceE.J. Woltering1,2, I.M. Witkowska2, R. Schouten2, J. Harbinson21Wageningen University & Research Centre, Food & Biobased Research, Bornse Weilanden 9, 6708 WG, Wageningen, The Netherlands2Wageningen University, Horticultural Supply Chains, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands V Postharvest Unlimited, ISHS International Conference, 10-13 June 2014, Cyprus, http://web.cut.ac.cy/postharvest/ Picture by www.la-razon.com Key wordsPoscosechapostcosecha???????? postharvestna-oes???????? ?? ??? ????????????? ????????????? post-r?colte???????? ???? ?? ??????????????????????????? na-oogst????? post-raccolta???????? Obr?bka pop?s-colheita???????? ??????????????? hasat sonras????????????????? Ernte??????????????? ???? ??????????????????? postcollita??? poskliz?ov???? ??????????????????? nakon branja???????? pozberov頠 ???????? obdelovanje zemlje po???? post-colleita????? ?????? pascapanen?il?onn postharvest???????? ????? p?c ra?as??? derliaus apdirbimas po??? lepas tuai??? ?? ?? ???????????? post-recoltare???????? ?????? ??????????? ??????????????????? ??????????????? ???????????????? sau thu ho?ch???????? ????????????????????? zangemva kwenkathi yokuvuna ???????? lechuga?????? lettuce?? blaarslaai?? ?????? ???? laktuko?? laitue?????? ????????? ??????????? sla?? lattuga?? sa?ata?? alface?? ?????-??????? marul?? ???????? ?????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????????????????? ?????????????????? ????????????? salat?