The first step in preparing limes for market involves cleaning of the fruit surface to remove dirt, sooty mould, scale, spray residues, etc. In small-scale operations, the fruit can be cleaned by putting the fruit in a wash tank and gently rubbing with a soft cloth or soft brush. The wash water should be properly sanitized with 150 ppm hypochlorous acid (household bleach) and maintained at a pH of 6.5. 150 ppm is equal to 2 oz of household bleach (such as Marvex) per 5 gallons of water, or .3 litres of bleach per 100 litres of water. The water should also contain soap or detergent.

Steel drums can be used to make a simple washing stand. The drums are cut in half, fitted with drain holes, and all the metal edges are covered with split rubber or plastic hose. The drums are then set into a sloped wooden table. The table top is constructed from wooden slats and is used as a drying rack before packing.

In larger-scale operations, limes may be cleaned by passing the fruit along with a series of revolving roller brushes. Initial rotating brushes will remove most debris, after which soap or detergent is sprayed onto the fruit to enhance cleaning as the fruit continues across the brushes. Adequate cleaning usually requires about 30 seconds on the brushes, rotating at about 100 rpm. The fruit is thoroughly rinsed as it passes over the last of the brushes and the excess water on the surface can be eliminated with sponge rubber rollers. A postharvest fungicide can be applied as an overhead spray following washing and water elimination. A spray wax application can also be made at this time.

Grading
Limes should be sorted and graded immediately following cleaning. The main fruit characteristics used in grading limes are size, colour, shape, and appearance of the peel. The minimum size requirement for marketing limes in the domestic market is a weight of 75 gn and diameter of 4 cm. There is no maximum limit for weight and diameter. Further sorting of limes into different size categories for domestic market sales may be worthwhile if a premium price can be obtained for certain sizes. For export markets, sizing of the fruit is essential. Limes should be separated into small, medium, and large sizes. In most small-scale operations, manual sizing is done with the use of standard size gauges made of wood or plastic. Examples of the different market sizes should be placed within view of the workers for easy reference. Mechanical sizers are also available for larger-scale operations using conveyors fitted with rubber belts having openings of different sizes, with the smallest openings placed first and the largest openings put at the end of the line.

Within the size categories, the fruit should also be separated according to peel colour and the number of surface blemishes. Green and yellow coloured fruit should not be mixed in the same container. The limes in each carton should be uniform and consist of the same cultivar, quality, size, and grade. The fruit should not have any noticeable peel scarring, insect injury, decay, wounds, sunscald, oil spots, and stylar-end breakdown. The fruit should also have a well-formed uniform shape typical of the cultivar. High-quality limes shiny, uniformly coloured, and free of surface injury, shrivelling, and decay.

Waxing
Limes have a very thin peel cuticle (waxy covering) and are quite susceptible to moisture loss during storage. In addition, much of the lime’s natural wax may be removed during washing. Limes will benefit significantly from a postharvest wax application, which will reduce the amount of dehydration during storage and give a shine to the fruit surface. The wax may be applied by hand rubbing, or mechanically as a foam, dip, spray or brush wipe. The wax is usually applied with water using an emulsifier, such as soap, to keep the wax soluble. Water-emulsion waxes do not require a completely dry fruit surface before application. Spray application is most commonly used in larger-scale operations, using a pair of travelling spray nozzles over a bed of slowly rotating (not more than 100 rpm) horsehair-type brush rollers. The wax coating can be detrimental to limes if it is applied too thick. This may restrict oxygen absorption and cause off-flavour development of the juice. A fungicide can be incorporated in the wax to prevent postharvest decay. Recommended fungicides are thiabendazole or imazalil (2000 ppm) or benomyl (1000 ppm). The fungicide concentration incorporated in the wax is double the amount recommended in the wash or spray water.