Effect of process technology on the nutritional, functional, and physical quality of grapefruit powder

Abstract

The health properties of fruit are widely known. Powdered fruit may be a practical format to be offered to the consumer. Nevertheless, the process used to obtain the powder must ensure the maximum retention of the bioactive compounds and the functional value of the fruit while retaining adequate physical properties. The aim of this study was to compare freeze-drying and spray drying as the drying technologies to obtain grapefruit powder. The obtained results allow freeze-drying to be proposed as a better technology than spray drying in order to obtain a product with a higher content of vitamin C and total carotenoids. Moreover, all of the edible part of the fruit is used in this case, so a greater quantity of healthy compounds is preserved and by-product generation is avoided. Adding about 6 g water, 4 g Arabic gum and 0.6 g bamboo fibre/100 g grapefruit pulp is recommended before freeze-drying.

Phytochemical content and antioxidant activity of grapefruit (Star Ruby): A comparison between fresh freeze-dried fruits and different powder formulations

“…Six formulations (4 for FD and 2 for SD) containing different proportions of the shell materials (AG and BF) or water content, selected according to a previous study (Agudelo, Igual, Camacho, & Martínez-Navarrete, 2016), were prepared (Table 1). For FD formulations, AG and BF were mixed with ground grapefruit and afterwards the samples were placed in aluminium pans (approximately 250 g in 0.5 cm thickness by pan) and immediately frozen at À45 C (Liebherr Mediline, LCT2325, Germany) for 48 h before freeze-drying in a Telstar Lioalfa-6 Lyophyliser at 0.021 Pa and À59 C. The obtained cakes were ground (Kenwood, CH 580, Spain) and sieved to obtain powder with a particle size lower than 0.7 mm.…”

“…Although spray-drying process caused a significant (p < 0.05) decrease in the content of ascorbic acid, the retention levels were high. Despite the high temperature used in the process, the drying occurs instantaneously, so that the sample does not stay in contact for a long time with the high temperature, which can guarantee the preservation of sensitive compounds (Agudelo et al, 2016). Moreover a slightly greater protective effect was observed when arabic gum and bamboo fiber were added together (SD 1 ), with 94% of retention for 92% in the sample containing only AG (SD 2 ).…”

Sensory characterization of juice obtained via rehydration of freeze‐dried and spray‐dried grapefruit

“…In order to improve the stability of the dehydrated grapefruit, gum arabic (Scharlab, Sentmenat, Spain) and bamboo fibre (VITACEL ® , Rosenberg, Germany) were added to the fruit prior to freeze‐drying or spray‐drying. The amount of both biopolymers used in this study, which is detailed in the following subsections, corresponds to the results of a previous study; this concentration was considered as the one that permitted the obtaining of freeze‐dried and spray‐dried grapefruit powder of the highest nutritional and sensorial quality; this is based on its colour, mechanical properties, hygroscopicity, solubility, total phenols, flavonoids, vitamin C and antioxidant activity, and also the product yield in the case of the spray‐dried product.…”

“…The water content of the puree was determined before. 4.2 g of gum arabic and 0.58 g bamboo fibre were added to 100 g puree, following the reported formulation optimized in an earlier study . The samples were then distributed on trays, forming a layer 0.5 cm thick, and were frozen at −45 °C (Liebherr Mediline 7083 207–00, Austria) until they were freeze‐dried (Telstar Lioalfa‐6, 10 −2 Pa and −55 °C in the condenser, 48 h).…”

“…Previously washed, peeled and cut fruit was liquidized in a food processor (De'Longhi, Treviso, Italy) and its water content was analysed. Gum arabic (4 g) and bamboo fibre (2 g) were totally dissolved in distilled water (100 g) and mixed with the liquidized grapefruit in a ratio of 1:1 (solute–water:liquidized product) . A spray dryer (B‐290, Büchi, Oldham, UK) was used to obtain the powdered product.…”