Semiconductor gas sensors can be widely used in food industry and agriculture. Measurements of ethylene concentration in vegetable stores and greenhouses allow the control of fruit ripening, whereas detection of H2S, mercaptans, amines may be used to control of meat, fish and vegetable freshness. In this work we present a new generation of semiconductor gas sensors based on the combination of micromachined silicon substrates [1] and highly sensitive layer of ZnO nanoparticles with controlled morphology (Fig. 1). ZnO nanoparticles of different size and nanorods with various length-diameter ratio were obtained following a controlled hydrolysis reaction of an organometallic precursor, namely the biscyclohexyl zinc, in the presence of long-chain amines as ligands [2]. Zinc oxide size and morphology was controlled by a choice of ligand, precursor concentration and water level. ZnO nanopowders were deposited on optimized micromachined silicon substrates with very low power consumption (Fig. 2) by a generic ink jet method. High quality and micron thick layers can be obtained with a low defect level (no cracks, no delamination). Gas sensitivity to reducing gases and air stability are presented in comparison with SnO2 sensitive layers. Gas sensors based on ZnO nanorods show high sensor response to ethylene and ammonia, whereas their response to CO and C3H8 is considerably lower.