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UV Process Validation
Published in Tatiana Koutchma, Ultraviolet Light in Food Technology, 2019
Pectins are a group of colloidal carbohydrates naturally present in fruit juices. They act as natural stabilizers and give the fruit juice a consistency that is generally referred to as “body” by the fruit juice industry. Pectinesterase is the indigenous enzyme that degrades the pectin colloid and decreases the cloud stability of the juice. The titration method using a pH stat system or the colorimeteric method developed by Rouse and Atkins (1955) can be used to measure the activity of pectinesterase in citrus juice. Standard tests such as the official methods from AOAC or the Department of Citrus, Florida must be employed to analyze the physical, chemical, and nutritional attributes of the juice. Sensory evaluation by expert- and consumer-panels is used to document changes in sensory profile and consumer acceptance. Analysis of the aroma profile by gas chromatography is employed to supplement the organoleptic information collected from sensory evaluation.
Combining osmotic–steam blanching with infrared–microwave–hot air drying: Production of dried lemon (Citrus limon L.) slices and enzyme inactivation
Published in Drying Technology, 2018
Lemon is a good source of ascorbic acid and it is widely available in tropical countries. Enzymes are the prime reason for the deterioration of lemon. Enzymatic activities increase as a consequence of the increased permeability that results from tissue disruption and mixing of enzymes and substrates that are otherwise sequestered within vacuoles.[1] Peroxidase and pectinesterase are the major active enzymes present in peel and pulp of the lemon, respectively. The presence of a residual enzyme in the processed product may cause quality damage like color, texture, and nutritional losses. Therefore, the processing and storage of lemon are difficult without enzyme inactivation.[2] Blanching is the common heat treatment to inactivate the enzymes and remove the entrapped air. Despite, blanching has a detrimental effect due to the undesirable quality changes caused by the degradation of organoleptic and nutritional properties.[3,4] The loss of ascorbic acid from the lemon is higher in water blanching than steam blanching. Pronounced leaching of constituents is reported during high-temperature water blanching of fruits and vegetables.[5] Use of chemical additives can decrease the heat resistance of the enzymes. Researchers found that calcium ions have a great effect on pectinesterase activity. Calcium ions protect the cell wall and prevent the destruction of cell compartments, thereby avoiding the mixing of substrates and enzymes.[6] The increase in calcium concentration decreases the temperature stability of the pectinesterase. Thermal treatment between 65° and 90°C for 5 min completely inactivates pectinesterase.[7] Also, few researchers have found ultrasound as an alternative to other traditional heat treatment methods to inactivate enzymes.[8,9]