Effects of Blanching on Flavanones and Microstructure of Citrus aurantium Peels

Abstract

Water and steam blanching were investigated as pretreatments of bitter orange peels in order to modulate their bitterness before further formulation processing such as osmotic treatment and drying. The fruit pieces were water blanched at 95°C for 10 min and at 85°C for 60 min and steam blanched at atmospheric pressure during 5 min. The kinetics of water inflow and bitter flavanone losses were established from the variation of moisture and bitter compound contents during the blanching process. The whiteness and the citrus color indexes were adopted to evaluate respectively the color of the flavedo and the albedo. Thin sections of fresh and treated peels were resin embedded for light microscopy evaluation and optical porosity determination. Results revealed that water blanching could partially debitter the peels by removing about 38 and 48 % of bitter flavanones (naringin, neohesperidin, neoeriocitrin) respectively at 95 and 85°C. The citrus color index and the whiteness index decreased during the process denoting a flavedo discoloring and an albedo darkening. By contrast, the steam blanching showed good retention of bitter compounds. The color of the flavedo was unaffected by steaming while the whiteness index decreased.At microscopic level, the water-blanched peels exhibited an extreme swelling of the cell walls and slight disintegration of the tissue. Contrariwise, the steam blanching maintained the structure of the peels and brought about the shrinkage of the albedo tissue and the decrease of porosity.

Blanching Pre-Treatment Promotes High Yields, Bioactive Compounds, Antioxidants, Enzyme Inactivation and Antibacterial Activity of ‘Wonderful’ Pomegranate Peel Extracts at Three Different Harvest Maturities

“…During processes such as drying, freezing, and/or storage of peel, enzymatic reactions cause deterioration in the phytochemical and nutrient profiles reducing their content and quantity for value addition [19][20][21]. Effective methods of preserving these secondary metabolites and reducing their oxidation are crucial and still sought after.…”

“…Hot water blanching is a pre-treatment step used prior to drying and aids in the inactivation of quality changing enzymes such as polyphenol oxidase (PPO) and peroxidase (POD). These enzymes lead to the degradation reactions that cause breakdown of nutrients and phytochemicals, off-flavours, odours, and undesirable texture and colour in vegetables and fruits [3,[19][20][21]. The blanching technique is well recognised as a valuable and inexpensive method to inactivate browning enzymes such as PPO and POD, increasing extractability by loosening cellulosic structures within the peel [3,19,20,22,23].…”

“…Blanching is a practical step to produce high-quality value-added products from peel waste but there is no single method that is being applied routinely across different species and cultivars. Its effects may depend on the type and size of plant material, thermal stability of different phytochemicals, location of phytochemicals within the plant structure, enzyme activity, and cultivar differences [3,[19][20][21]23,25].…”

The Effect of Pre-Drying Treatment and Drying Conditions on Quality and Energy Consumption of Hot Air-Dried Celeriac Slices: Optimisation

“…Furthermore, the removal of intercellular air affected the samples' reflecting properties due to hot water blanching, resulting in translucent vegetables, and resulting in this noticeable shift of blanched samples' colour characteristics [76]. Ben Zid et al [77] mentioned the same prediction on blanched albedo (white part) of citrus peel where it became transparent and darker due to blanching water absorption and a decrease of WI was observed. Moisture content affected the reflectance colour values of dried samples [82].…”

Isolation and characterization of naringinase enzyme and its application in debittering of Pomelo juice ( Citrus grandis ): A comparative study with macroporous resin

“…The pomelo juice has the prime bittering component, such as naringin, narirutin, neoeriocitrin, eriocitrin, neohesperidin, and hesperidin, with a level of 245.63-393.96 mg/L which are not desirable in fruit processing industries as they reduce the consumer acceptability (Pichaiyongvongdee & Haruenkit, 2009). Processing techniques like blanching (Zid et al, 2015), application of adsorptive materials, for example, cellulose triacetate (Chandler & Johnson, 1977) and cellulose esters (Barmore et al, 1986), chemical methods with the use of β-cyclodextrin (Konno et al, 1981), resins (Gupta et al, 2020;Kola et al, 2010;Mishra & Kar, 2003;Singh et al, 2016), mixed with sugar syrup (Kore & Chakraborty, 2015), lye peeling (Kore & Chakraborty, 2015), pH adjustment (Kore & Chakraborty, 2015), hot water treatment (Kore & Chakraborty, 2015), and the combination of sucrose and citric acid (Guadagni et al, 1974) were employed for debittering. Polystyrene divinylbenzene, resin (Mishra & Kar, 2003), poly (vinyl alcohol) (PVA), and cryogel (Busto et al, 2007) were also used successfully for the removal of bitterness from the juices; however, the physical and chemical methods are not always welcomed by the juice processing industries, as these techniques had several drawbacks including loss of chemical components like acidity, vitamin C, and soluble solids.…”