Development of a 3D-printable vegetable-based, highly nutritious and tasty snack

This study focuses on the development of a stable, vegetable-based snack product with improved nutritional and sensory quality and attractive shapes for young children. Frozen zucchini (Cucurbita pepo), tomato, carrot and onion, with added olive oil and water, were processed into purees and analysed for flow behaviour for an extrusion-based 3D food-printing application. To improve viscosity, xanthan gum (XG) and LBG (locust bean gum) were tested separately and combined; the best combination was 0.6% XG and 1% LBG.  A final puree formulation with good extrusion consistency, 3D printability, and good shape retention was obtained.

As the colour and taste were not attractive enough, replacement of at least part of the zucchini by other types of squash varieties, squash (Cucurbita moschata) and chuchu (Sechium edule) was next studied. A vegetable puree formulation was optimised by using a Simplex Lattice Mixture Design and Response Surface Methodology, where the independent variables were x₁, zucchini; x₂, squash; and x_3,  chuchu, and the dependent variables were the responses Y₁, aroma; Y₂, aspect; Y₃, taste; Y₄, texture; Y₅, overall opinion; Y₆, aftertaste; and Y₇, viscosity. A sensory panel evaluated the first 6 responses, and Y₇  was evaluated by a viscometer. Based on polynomial models obtained for each response, numerical optimisation was conducted to produce the formulation with the highest sensory scores and a viscosity restricted within the range for 3D-printability.

With the optimised formulation, the vegetables were pressure-cooked under different time-temperature combinations to study the effect of thermal processing retention on the most important nutrient, b-carotene.  The optimum cooking conditions,110°C for 2 min, showed the highest b-carotene retention (3.1127mg/g). The optimised vegetable puree formulation, cooked at the optimum condition, was then successfully 3D-printed into two different shapes, a dinosaur and a flower tower, and freeze-dried for shelf-life extension and shape stability. The result of this study proved that by using several sequenced and optimised processes, a healthy (highly nutritious), visually appealing to children, and tasty vegetable-based snack could be developed.