Effects of Hydroponic Cultivation on Baby Plant Characteristics of Tetragonia tetragonioides (Pallas) O. Kunze at Harvest and During Storage as Minimally Processed Produce

Tetragonia tetragonioides, or New Zealand spinach, is a widespread halophyte native to eastern Asia, Australia, and New Zealand, and naturalized in some Mediterranean regions. This underutilized vegetable is consumed for its leaves, raw or cooked. For the first time, we investigated the feasibility of using whole baby plants (including stems and leaves) as raw material for ready-to-eat (RTE) vegetable production. Our study assessed Tetragonia’s suitability for hydroponic cultivation over two cycles (autumn–winter and spring). We investigated the impact of increasing nutrient rates (only water, half-strength, and full-strength nutrient solutions) and plant densities (365, 497, and 615 plants m−2 in the first trial and 615 and 947 plants m−2 in the second) on baby plant production. We also analyzed the plants’ morphological and biochemical characteristics, and their viability for cold storage (21 days at 4 °C) as a minimally processed product. Tetragonia adapted well to hydroponic cultivation across both growing periods. Nevertheless, climatic conditions, plant density, and nutrient supply significantly influenced plant growth, yield, nutritional quality, and post-harvest storage. The highest plant density combined with the full-strength nutrient solution resulted in the highest yield, especially during spring (1.8 kg m−2), and favorable nutritional characteristics (β-carotene, Vitamin C, Fe, Cu, Mn, and Zn). Furthermore, Tetragonia baby plants proved suitable for minimal processing, maintaining good quality retention for a minimum of 14 days, thus resulting in a viable option for the RTE vegetable market.