Fortified and freeze-dried kiwi fruit (Actinidia deliciosa): quality and sensory assessment

Abstract

Kiwi fruit (Actinidia deliciosa) (KF) is one of the best fruits available due to its large amount of nutrients. Despite its many health benefits, there are no previous reports on its preparation in other readily ingestible forms. The objective of the present study was to make a new food product from KF. The KF pulp was fortified and blended with several raw materials (such as rice flour and oat flour) using a stepwise short time addition and mixing methodology since this avoids unwanted biochemical and chemical reactions. The blended and reduced moisture KF paste was freeze-dried on a round silver coated steel plate (RSCSP), supplying the heat of sublimation using a newly designed cubic heater. The freeze-drying (FD) time was 4.5 h and the drying kinetics were studied using four established models. The effective moisture diffusivity (Deff) during FD (at 50 °C) was 1.532 x 10-6 m2/s and the activation energy (E) estimated for the FD was 28.35 kJ/mol. The freeze-dried sample was ground and placed under vacuum to reduce the weathering effects. The quality of the stored product was evaluated using the proximate analysis, physicochemical analysis and a sensory evaluation using a hedonic scale. The raw, fresh KF had a moisture content of 85.07% and the final freeze-dried product one of 3%. The carbohydrate, total sugar, protein, fat, total ash, crude fibre and vitamin C contents of the final product increased by 563%, 400%, 355%, 386%, 672%, 106%, and 117% respectively. Of the 66 panelists, the % consumer acceptances for the different attributes were: sweetness (68.18%), sourness (90.91%), saltiness (100%), bitterness (100%), flavour (95.45%), texture (77.27%) and overall acceptability (81.82%). Using conventional freeze-drying (CFD) for blended KF pulp without fortification, with the same RSCSP and the same cubic heater for sublimation, the drying time was found to be 7 h to reach the same final moisture content of 3%.

Influência da radiação ultravioleta e aditivos na conservação de kiwis minimamente processados

“…O kiwi possui alto teor de umidade, sendo um produto altamente perecível (Chin et al, 2015). Portanto, é desafiador manter o produto fresco, pois perde gradualmente o frescor após alguns dias (Chakraborty et al, 2020). Segundo Heiffig et al (2006), os kiwis minimante processados possuem vida de prateleira entre seis e nove dias.…”

Recent Developments in the Hybridization of the Freeze-Drying Technique in Food Dehydration: A Review on Chemical and Sensory Qualities

“…According to the available literature, freeze-drying is an ideal method for food dehydration, allowing for long shelf-life, acceptable nutrient retention, and minimal shrinkage that creates a porous product with excellent rehydration capacity and aqueous solubility, soft texture, and reduced weight for storage [ 1 , 2 , 5 , 6 ]. Most degradative activities, including protein degradation, microbial action, enzymatic reaction, and non-enzymatic browning, are constrained or even prevented by the absence of liquid water and the low temperature during freeze-drying [ 7 ]. In addition, the concentration of oxygen available in the freeze-drying chamber decreases due to the high vacuum conditions, which can significantly slow down the deterioration of heat- and oxygen-sensitive components like vitamin C, anthocyanidin, and carotenoids [ 8 ].…”

“…The effects of operational factors in freeze-drying (temperature, vacuum pressure, and time) on the conservation of the key functional compounds in food-based plants (i.e., fruits, vegetables, and herbs) are extensively discussed in the literature [ 1 , 4 , 7 ]. Depending on the selected parameters, the nutritional content of the final product may increase or decrease during the freeze-drying process.…”