Drying Kinetics and Quality of Dehydrated Cranberries Pretreated by Traditional and Innovative Techniques

Abstract

The aim of this study was to analyze the impact of traditional and combined pretreatment on dehydration kinetics and quality of dried swamp cranberries. Fruits were blanched, cut, or treated by combined technique consisting of blanching and application of pulsed electric field. Afterwards, fruits were subjected for osmotic dehydration (OD; 72 hr) in 61.5% sucrose solution or in ternary solution consisting of 30% sucrose with 0.1% addition of steviol glycosides to ensure similar sweetness of both mixtures. In the case of samples treated by combined method, OD was enhanced during first 30 min by sonication. Partially dehydrated cranberries were air dried at 70 °C. The quality of dehydrated fruits was assessed by the means of phenolics content, anthocyanin content, flavonoid content, vitamin C content, water activity, and color. Blanching decreased drying time by 48% to 50% in comparison to cutting. Utilization of combined method reduced drying time of cranberries up to 55% in comparison to cut samples. Water activity of all samples was below 0.6. Blanched samples or blanched and then treated with pulsed electric field and ultrasound contained more anthocyanins and flavonoids and less sucrose than cut samples. Practical Application According to current trends in food and beverage industry, consumers seek for products which does not contain excessive amounts of sugars, salt, or fats. Dried cranberry fruits are rich in bioactive compounds and need to be osmotically dehydrated in sugar solutions to make the taste of the final product acceptable. Osmotic dehydration is also carried out to decrease time of drying, which is one of the most energy intensive processes. Therefore, there is a need to develop a technology with potential to maintain the bioactive compounds, reduce sugar content in comparison to traditionally process fruits, and enhance the kinetics of drying.

The Effect of Traditional and Non-Thermal Treatments on the Bioactive Compounds and Sugars Content of Red Bell Pepper

“…This can be explained by formation of derivatives of phenolic compounds that improves antioxidant activity [ 5 ]. This operation is applied before such processes as cutting, peeling, freezing [ 5 ], osmotic dehydration or drying [ 18 ].…”

“…Ultrasound (US) is one of the non-thermal technologies which can be used for inactivation or activation of the enzymes, cleaning, decontamination of the surface, enhancement of extraction, osmotic dehydration, freezing, drying, etc. [ 18 , 19 ]. The US treatment shows promising features as a method supporting food production processes.…”

“…Generally, the pre-treatment, applied by traditional or non-thermal methods, can performed to obtain ready to eat minimally processed product or to precede proper processing such as drying, freezing, etc. [ 18 , 29 ]. In recent years, the combination of different pretreatment with each other and with other processes is reported in the scientific publications in order to obtain specific purposes and to keep the high quality of the product [ 30 ].…”

“…In recent years, the combination of different pretreatment with each other and with other processes is reported in the scientific publications in order to obtain specific purposes and to keep the high quality of the product [ 30 ]. For example, the combination of thermal and non-thermal processes such as blanching in water, PEF treatment with sonication, which was subjected to osmotic dehydration and hot-air drying of cranberries allowed to reduce the drying time in the range from 48 to 55% in comparison to traditionally treated material [ 18 ]. Tao et al [ 31 ] enhanced the convective drying and reduced the process up to 83.4% by applying blanching coupled with contact sonication.…”

Oligosaccharides and Complex Carbohydrates: A New Paradigm for Cranberry Bioactivity

“…Heat treatments may lead to increased monomeric flavonoid concentrations due to the inactivation of intrinsic degradative enzymes and the degradation of heat-susceptible polyphenolic macromolecules [54,58,61,81]. Reverse osmosis used for juice concentration and the osmotic dehydration process used for the production of sweetened dried cranberries (SDC) may both lead to the unintentional loss of flavor components and other osmotically mobile small molecules from the final product [81][82][83][84], or may result in the transfer of compounds from juice to SDC products [42]. The jelly making process involves heat and the addition of sugar that leads to the crosslinking of pectins and hemicelluloses to form a gel [43][44][45].…”