Influence of growing techniques of low environmental impact on the qualitative characteristics of frozen spinach [Spinacia oleracea L. - Marches (Italy)]

biomasa biomass biomassa biomasse blanchiment blanching blanqueo calidad color colore colour compost composts couleur cultural methods engrais organique ensayos de variedades environmental impact espinaca fertilizzanti organici feuille foglie frozen products hojas impact sur l'environnement impacto ambiental impatto ambientale largura leaves length longueur lunghezza marcas (italia) marche marches (italie) marches (italy) metodi colturali mode de culture nitrate nitrates nitrati nitratos nitrite nitrites nitriti nitritos organic fertilizers peciolo petioles piccioli prodotti congelati productos congelados prove varietali quality spinach spinacia oleracea variedades varieties variety trials