Novel Ingredients Based on Grapefruit Freeze-Dried Formulations: Nutritional and Bioactive Value.

Marta Igual,Claudia Agudelo,Laura Cebadera,Nuria Martínez-Navarrete,Rosa Mᵃ Cámara,Montaña Cámara

doi:10.3390/foods8100506

Abstract

Grapefruit is a fruit with interesting nutritional value and functional properties, but a short life. Freeze-drying (FD) is a valuable technique as it produces high-quality dehydrated products. This study is aimed to obtain new food ingredients based on freeze-dried grapefruit formulated with high molecular weight solutes (gum arabic and bamboo fiber) in three different proportions (F1, F2, and F3). To improve the FD, a mild microwave drying pre-treatment was applied. Influence of the water content and the presence of high molecular weight solutes on freeze-drying kinetics was tested by Midilli-Kucuk and Page models. The best FD kinetic model fit on grapefruit powders were Midilli-Kucuk for F2 and F3, and Page for F1, and the adequate freeze-drying times for F1, F2, and F3 were 24, 16, and 18 h, respectively. Final samples were evaluated for nutritional and antioxidant capacity. Gum arabic and bamboo fiber present a protector effect, which results in a significant antioxidant capacity due to the protection of flavonoids and antioxidant vitamins. These novel food ingredients could be of great interest for the food industry in order to develop foods with improved antioxidant capacity as well as enriched in natural fibers and/or micronutrients.

Highlights

Fruits, independent of their nutritional value, are generally recognized as important sources for a wide array of phytochemicals, which individually, or in combination, may benefit human health, are considered bioactive compounds [1].Citrus fruits are an important source of physiologically active substances that fulfill, like essential nutrients, a beneficial function for health and contribute to reduce the incidence of certain chronic diseases
All the analyses described below, except the soluble solid content, were carried out in triplicate on grapefruit freeze-dried powdered samples
The average values of water and soluble solids mass fraction (◦ Brix) and water activity of fresh grapefruit used as raw material were xw = 87.82 (0.02) gw /100g, xs = 11.0 (0.2) gss /100 g and aw = 0.989 (0.003)

Summary

Introduction

Independent of their nutritional value, are generally recognized as important sources for a wide array of phytochemicals, which individually, or in combination, may benefit human health, are considered bioactive compounds [1]. Citrus fruits are an important source of physiologically active substances that fulfill, like essential nutrients, a beneficial function for health and contribute to reduce the incidence of certain chronic diseases. The consumption of citrus fruits in the diet, acquires greater interest due to its high content in water and low caloric intake, at the expense of carbohydrates, and with little content in lipids and proteins [2]. Freeze-drying (FD) applied to food preservation is a valuable technique to produces high-quality dehydrated products with very low final water content. The solid state of water during FD protects the primary structure and minimizes the changes to the shape of the product, with a minimal

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