how to keep lettuce crisp

{"cid":"91191364","title":"Lettuce \/ Potato Chip Slicer Machine 220 \/ 380V Voltage 70KG Net Weight","imgUrl":"https:\/\/img.chinax.com\/nimg\/f5\/19\/924f24fc006793b1c8aa89c38b8a-200x200-1.jpg","attrs":{"Price":"Negotiable","Brand Name":"XUANHUA","Model Number":"QC-300","Minimum Order Quantity":"1","Delivery Time":"5-20 working days after received payment","Certification":"CE","Place of Origin":"CHINA","Payment Terms":"L\/C, T\/T, Western Union","Supply Ability":"200 sets\/month","Packaging Details":"Wooden Packing or according to your requirements","Product Name":"Fruit and vegetable cutting machine","Finished Product":"Slices, Chipps, Cubes","Stick Blade":"1~13 mm","Slice Blade":"3*3~12*12mm","Cube Blade":"0.87m2","Capacity":"300~600 Kg\/h"}}

{"cid":"91178288","title":"YIERYI IGS-38 Smart Indoor Hydroponic Garden System with 15-Pot Capacity Full-Spectrum LED and Automatic Watering","imgUrl":"https:\/\/img.chinax.com\/nimg\/54\/fc\/089017019ba3116cffd920b947ed-200x200-1.jpg","attrs":{"Price":"$33-35","Brand Name":"YIERYI","Minimum Order Quantity":"10","Place of Origin":"Guangdong, China","Type":"Growing Machine","Voltage":"220 V","Display Type":"LED","Plant Capacity":"15 plants","Lamp Height":"210mm to 350mm","Watering Interval":"30 minutes","Footprint Dimensions":"36\u00d718 cm","Light Type":"Full-Spectrum LED","Light Colors":"Red, Blue, White","Included Seed Pods":"15","Nutrient Type":"Dual-bottle (A+B)","Operation Type":"Touch-control panel","Water Circulation":"Automatic","Growth Medium":"Hydroponic","Product Model":"IGS-38"}}