Apple slices, canned

Infer Apple slices can be kept from browning by brushing them with lemon juice. Infer what role lemon juice plays in this case. 

Native pectin esterases can be used for protecting and improving the texture and firmness of several processed fruits and vegetables these include apple slices (53), canned tomatoes (54), cauliflower (55), carrots (56), potatoes (56), beans (57) and peas (91). 

In addition, fhiit and vegetables can be minimally processed (washed, pealed, cut, diced, stripped, chopped, etc.) in order to provide ready to eat or ready to use products (salad mixes, apple slices, carrot sticks, diced potatoes, etc.). These minimal processing treatments damage the plant surface and induce changes in phenolic metabolism and phenolic antioxidant composition. 

Pressure test" is something of a misnomer, as it is a force, equal to the resistance to shear and crushing under the slightly convex 7/16-inch diameter tip, that is measured and not pressure in the usual physical or engineering sense. Its widespread use can be explained by its simplicity and easy adaptability to use in the orchard or plant. Furthermore, it does provide a reasonably good correlation - somewhat dependent on variety -with both peelability and final product texture in the case of apple slices or sauce and with pressability for cider and juice. 

Osmotic dewatering can be facilitated by decreasing mass transfer resistance. This can be done either by circulation of solution or by slow movement of food. Circulation of solution is done by installation of circulation pump to a vessel in which basket with food is immersed. Movement of food in the solution is done by vibration (Figure 32.15) or by a conveyor (Figure 32.16). The latter solution is used in Poland in the processing of apple slices [168,169]. 

Li et al. (2010) investigated the microwave-assisted convective drying of apple slices with time-adjusted power in feedback temperature control. Three desirable temperatures of 75, 65, and 55 °C were chosen, and the corresponding maximum power requirements were set at 400, 300, and 240 W, respectively. The relationships of power versus time and of power versus moisture content (d.b.) can be described by the following equations, respectively ... 

Apples are canned, sliced or cubed, eis pie filling or eis applesauce. Slices are usually packed without symp. However, applesauce is the most important canned apple product... 

The waxy material present in apple skin which is sometimes removed by dewaxing with hot isopropyl alcohol vapor in order to reduce the amount of peel lost during the processing of apples into canned slices or juice. Dewaxing of apples makes it possible to remove the peel with a lye solution. 

To prevent non-enzymatic browning, the fruit can be dipped in a 5% solution of citric acid (or in lemon juice). This is especially advisable in the case of sliced and diced apples where the acid content is low. The acid allows the light colour to be retained, while at the same time improving the taste of the pieces of apple. The colour of the fruit can be made even lighter by adding ascorbic acid to the dip. 

Table XVI. Effect of Added Ascorbic Acid on Canned Sliced Apples"...

Sorbate combined with mild heat has a syneigistic effect with regard to microbial destruction thus, in the presence of 0.025—0.06 wt % sorbate, products such as apple juice, peach and banana slices, fruit salads, and strawberries can be treated with less severe heat treatments to extend shelf life (119,120). Sorbates increase the heat sensitivity of various spoilage fungi under varying conditions of pH and water activity (121—124). A similar syneigistic effect has been reported for the combination of sorbate with irradiation (125). 

Solutions of sugars are mostly used to dehydrate fruits and glycerol, starch syrup, and sodium chloride are used for vegetables [62,73,91,99]. Sucrose is the most frequently used substance [17,65,100-104]. The control of pH of sucrose solution is recommended for banana slices osmotic dehydration [105]. It was also shown that control of pH of sucrose solution affects the course of osmotic dehydration of apple and carrot [106]. Addition of ascorbic acid to sugar solution is practiced to minimize browning of fruit pieces during osmotic process [72]. Sucrose can be substituted in part by lactose [15]. 

Studies on banana tissue slices have shown that valine and leucine concentrations increase about threefold following the climacteric rise in respiration [10]. Radioactive labeling studies have shown that valine and leucine are transformed into branched chain flavor compounds that are essential to banana flavor (2-methyl propyl esters and 3-methyl butyl esters, respectively). As can be seen in Figure 4.6, the initial step is deamination of the amino acid followed by decarboxylation. Various reductions and esterifications then lead to a number of volatiles that are significant to fruit flavor (acids, alcohols, and esters). Recent work has shown that amino acids play a role in apple flavor as well. For example, isoleucine is the precursor of 2-methyl butyl and 2-methyl butenyl esters in apples [24,25]. An unusual flavor compound, 2-isobutylthiazole, has been found to be important to the flavor of tomato. It is hypothesized that this compound is formed from the reaction of 3-methyl-l-butanal (from leucine) with cysteamine. 

Since the middle of the 19 century, heat sterilization in cans and glass jars has been the most important process for fruit preservation. Undamaged, aroma-rich and not overripe fruits are suitable for heat sterilization. Aseptic canning is applicable only for fruit purees. Canned fruits used are primarily stone fruits, pears, pineapples and apples (usually apple puree). Strawberries and gooseberries are canned to a lesser extent. Canned fruits are produced in a large volume by the food industry and also in individual households. Cherries are freed from stone seeds and stems, plums/prunes, apricots and peaches are halved and the stone seeds are removed, strawberry calix is removed, gooseberry and red currant steins are removed, apples and pears are peeled and sliced. Specialized equipment has been developed for these procedures. 

Bake for 50 minutes, or until the crust is golden brown and the apples are tender. To test, poke a paring knife into the center of the pie to make sure the apples offer no resistance. If the pie needs a few more minutes, you can cover the crust with foil to keep it from browning too much. Cool slightly before slicing to allow the juices to set. 

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