Citrus peel

DisK Presses Figure 18-157 shows a disk press. The two disks, or press wheels, converge to a veiy narrow space at the bottom. This is the point of maximum compression, which can be more than 14 times the feed pressure. The press wheels have channels to cany the hquid from the dewatered product, and they are covered with a screen plate. Wheels 1.5 m (5 ft) in diameter are used on a large press that requires about 80 connected horsepower and produces just under 1 tonne/h (0.9 ton/h) of sohds (diy basis). Typical apphcations are fibrous materials such as coffee grounds, pineapple and citrus peels and wastes, alfalfa, and brewers spent grain. 

The other class of acrylic compatible tackifiers includes those based on ter-penes. Terpenes are monomers obtained by wood extraction or directly from pine tree sap. To make the polyterpene tackifiers, the monomers have to be polymerized under cationic conditions, typically with Lewis acid catalysis. To adjust properties such as solubility parameter and softening point, other materials such as styrene, phenol, limonene (derived from citrus peels), and others may be copolymerized with the terpenes. 

Mondello et al. (54) have developed some applications of on-line HPLC-HRGC and HPLC-HRGC/MS in the analysis of citrus essential oils. In particular, they used LC-GC to determine the enantiomeric ratios of monoterpene alcohols in lemon, mandarin, bitter orange and sweet orange oils. LC-GC/MS was used to study the composition of the most common citrus peel, citrus leaf (petitgrain) and flower (neroli) oils. The oils were separated into two fractions, i.e. mono- and sesquiterpene... 

Pectin is a long chain of pectic acid and pectinic acid molecules. Because these acids are sugars, pectin is categorized as a polysaccharide. It is prepared from citrus peels and the remains of apples after they are squeezed for juice. In the plant, pectin is the material that joins the plant cells together. When fungus enzymes break down the pectin in fruit, the fruit gets soft and mushy. 

Figure 11. Solid-state C NMR spectrum of hydrated cell walls from Citrus peel, with high content of methyl-esterified pectia...

Extrusion-cooking of cell-wall rich products (e.g. wheat bran, apple pomace, citrus peels, sugar-beet pulp, pea hulls.) led to an important solubilisation of polysaccharides of various types without extensive degradation of the polymeric structure. The possibility of obtaining gelled systems directly with the extruded pectin-rich materials was demonstrated. 

Many plant products are very rich in cell wall materials. Cereal brans, seed hulls, various pulps (including beet pulp), citrus peels, apple pomace... are typical exemples of such by-products (1,2). They can be used after simple treatments as dietary fibres, functional fibres or bulking agents, depending on the nutritional claims (2). They can be used also eis sources of some polysaccharides. 

Indeed, apple pomace, beet pulp or citrus peels contain pectins (3). Chemicals, enzymes, microorganisms, or physical treatments can be used for thextraction (4). 

However, the difference was more marked between the commercial pectins and the other pectins. The reasons for this discrepancy can be found either in differences in the values of the dm or in the origin of the raw materials. Indeed, a lower dm value can lead to firmer gels (19,20). However, the main reason is probably the fact that the citrus fibre used in this study was a commercial citrus (dietary) fibres of which the pectin quality may be lower than the citrus peels used by pectin industry. 

Extrusion-cooking increased very significantly the water-solubility of plant cell wall rich-materials. High amounts of pectins can be solubilised from sugar-beet pulp, citrus peels or apple pomace. 

The most studied system for agricultural waste recycling is their bioconversion into fiiels [1], such as ethanol production from sugarcane molasses, citrus peels [2] and whey [3],... 

To date, the structural features of pectic polysaccharides and plant cell walls have been studied extensively using chemical analysis and enzymatic degradation. In addition, research on isolation and physicochemical characterisation of pectin from citrus peels, apple peels, sunflower head residues and sugar beet pulp has been reported (2). However, the pectic polysaccharides extracted from wheat straw have only previously been reported by Przeszlakowska (3). The author extracted 0.44% pectic substances from Author to whom correspondence should be addressed. 

In a previous publication (1) we reported that the pretreatment of fresh fhiit waste using microwave heating ensured a better extraction of pectin, resulting in an increase in the yield of pectin from 10 to 50 %. It was established that this microwave pretreatment ensured retention of the degree of esterification of the extracted pectin, better expressed in citrus peels... 

The objectives of this study were to compare the yields of cold-pressed essential oil, water consumption, material balance and efficiency of the process in a typical citrus peel oil recovery plant with and without recycling system. The different emulsions and aqueous discharges from these processes were also characterized. 

Oligouronides production in a membrane reactor by enzymatic degradation of pectins from Citrus peel. A preliminary study... 

If acid-sensitive analytes (e.g., myclobutanil, propiconazole, tebuconazole, fiuotrima-zole, thiabendazole, carbendazim) are extracted from an acidic material (e.g., citrus peel, fmit powder), only low recoveries are obtained. If the pH of an aqueous homogenate of the material is <5, use Module E3, in which acids are neutralized before the extraction. 

Weigh 50 g of the ground hulled rice, citrus flesh, or tomato sample (20 g citrus peel or rice straw) into a 500-mL Erlenmeyer flask and extract with 250 mL of acetone (or methanol for rice straw) by shaking for 1 h. Filter by suction and collect the extract in a 500-mL round-bottom flask. Wash the cake with 100 mL of acetone (or methanol for rice straw) and filter off. Combine the filtrates and concentrate to around 2 mL at 40 °C with a rotary evaporator. 

With a fortification level of l-2mgkg recoveries of buprofezin from untreated hulled rice, rice straw, tomato, citrus flesh and citrus peel samples are 85, 97, 93, 87 and 75%, respectively. 

The limits of detection of buprofezin and /t-OH-buprofezin are 0.005 mg kg for hulled rice, tomato and citrus flesh and 0.01 mg kg for rice straw and citrus peel. 

In fruit penetration studies 8 pounds of fruit were first thoroughly scrubbed with warm 10% trisodium phosphate solution and then rinsed thoroughly with distilled water. Citrus fruits, if depth of penetration into the peel was of interest, were peeled in longitudinal sections with a buttonhook peeler and the albedo or white portion was separated from the flavedo or colored portion. The separated peel was placed in pie tins lined with waxed paper and dried in a forced draft oven at 65° C. for 16 hours. The dried peel was then crushed and steeped for 48 hours in a measured volume of benzene sufficient to cover the sample. If, on the other hand, only the total amount of DDT in the peel was of interest, the fruit was halved and juiced on a power juicer. The pulp was removed, the peel sliced, and the sample dried and treated as before. Thin-skinned fruits, such as apples, pears, and avocados, were peeled with a vegetable peeler, cores or seeds were removed, and the pulp was sliced in thin slices. Pulp and peel were then dried and treated in the same way as the citrus peel. The steeping completed, the samples were filtered through Sharkskin filter paper and the volume of benzene recovered was noted. 

As compared with the residues of DDT present within citrus peel (2), the relative significance of surface residues of DDT on citrus fruits is diminished by the fact that these are readily removed in large proportion by the usual packinghouse processing (5). 

The samples of citrus peel obtained by either method may have contained trace amounts of extra-surface DDT residues as differentiated from subsurface or penetrated... 

The importance of formulation on the penetration of parathion into the peel of citrus fruit is indicated in Table VI, the emulsified technical grade compound entering in greatest amount. This suggests the possibility of being able to formulate parathion in a manner which might effectively prevent the penetration of the compound into citrus peel but an attendant difficulty might be that its insecticidal effectiveness would be lessened. 

Bocco A, Guvelier ME, Richard H and Berset C. 1998. Antioxidant activity and phenolic composition of citrus peel and seed extracts. J Agric Food Chem 46 2123-2129. 

FW fresh weight mg/100ml, mg/100g dry material, Citrus peel and seeds... 

Pectin is used in foods in two forms, high methoxyl pectin and low methoxyl pectin. High methoxyl pectin is the form normally found in fruit while low methoxyl pectin is a chemically modified pectin. Pectins are acidic polysaccharides that occur in the cell walls of fruit. The commercial source of pectin is either citrus peel or apple pomace. The citrus peel is the residue from the production of citrus juices while apple pomace is the residue of cider production. Thus pectin is a by-product of either cider or fruit juice production. 

Chafer, M., Gonzalez-Martinez, C., Chiralt, A., and Fito, P. 2003. Microstructure and vacuum impregnation response of citrus peels. Food Res. Int. 36, 35-41. 

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