Juice quality

Pests iaclude rats, a severe problem ia some areas, wild animals, nematodes, and a number of iasects. The most severe iasect pests are the various types of borers, ie, the sugarcane borer, Diatrea saccharalis (F.) and the eldana borer, Pldana saccharina which cause damage first by boring iato the cane stalk, then by providing entry poiats for other diseases, and finally by reduciag cane and juice quality. 

MEHTA R A, CASSOL T, LI N, HANDA A K and MATTOO A K (2002) Engineered polyamine accmnnlation in tomato enhances phytonutrient content, juice quality and vine life . Nature Biotech, 20, 613-18. 

Although freezing will disrupt the cell structure of soft fruit and render it pulpy upon thawing out, any adverse changes to juice quality will be minimal and flavour and colour can be easily preserved by this treatment... 

In citrus fruits, where the outer skin or epicarp is a composite structure containing certain flavouring substances, it would be detrimental to juice quality if the fruit were subjected to direct pressure as is the case with the fleshy fruits, that is, soft fruits, pome fruits and stone fruits. Stone fruits, before being processed for juice separation, must first be separated from their stones, or pits, in order to facilitate ease of handling and to avoid unwanted notes in the finished... 

Limonoids are a group of chemically related triterpene derivatives found in the Rutaceae and Meliaceae. Limonin, a bitter member of the group, occurs widely in citrus juices. It has commercial significance because bitterness (excessive bitterness in the case of grapefruit) reduces juice quality. Dreyer (1) and Connolly et al. (2) have reviewed the chemistry and biochemistry of limonoids. 

More recently Maier et al. (3) published a comprehensive review of the limonoid constituents of Citrus and the impact of limonin bitterness on juice quality. This paper summarizes the chemical, biochemical and juice quality aspects of limonoids in Citrus (and related genera) and presents relevant advances since previous reviews. 

It exists both in the primary cell wall and in the middle lamella, the intercellular cement between cells. In this capacity it contributes significantly to structural integrity of fruits and. vegetables. As a soluble component of juice and an insoluble component of juice particulate material, pectin affects many facets of juice quality. 

Even at these levels, pectin influences juice quality, both positively and negatively, by its contribution to viscosity, gelation, and cloud stability. 

Clarified Juice. Some citrus juices, notably lime and lemon, are in demand as clarified products. Natural clarification, in combination with filtration, is often used to achieve a sparkling clear serum. However, native PE action is slowed by the high acidity of these juices, and may not give satisfactory cloud removal. In this instance, modified pectins can serve to enhance juice quality by removing cloud. 

In California, the color requirements are much different (58). The color of the peel is tied in with the juice quality, namely, the ratio which is the soluble solids divided by the acid content. Fruit having a bright peel color can be marketed with poorer juice quality (lower ratio) than that with poor peel color. This is a case where the best looking fruit may not be the best tasting. 

Several postharvest treatments to citrus fruits have been tested in an effort to improve the quality of the extracted juice. Bruemmer and Roe subjected citrus fruits to anaerobic conditions for periods of 20 to 32 hours at 32.2 to 43°C (228, 229). This treatment reduced the titratable acidity and increased the Brix-acid ratio by about 10%. The decrease in acidity was accompanied, however, by a 20-fold increase in ethanol (229). Since the soluble solids-acid ratio is a major criterion of citrus juice quality, this procedure, if perfected, could allow earlier harvesting of fruit and a more consistent supply of fruit during the processing season. Bitterness of products from navel oranges, lemons, and grapefruit is related to limonin content. A 3-hour treatment of fruit with 20 ul ethylene/1 of air lowered the limonin content, reduced bitterness, and the juice was judged more palatable than juice from untreated fruit (230). 

Several types of Brown extractors are used in the citrus industry throughout the world. The Model 400 produces a juice that is low in peel oil content and high in juice quality. The fruit is halved and the juice removed by a rotating reamer that exerts pressure to effect extraction. 

After drying, the healthy grape berries are separated from those that show rot, or that have been damaged by insects, and then they are pressed. The pressing of dried grapes is a very delicate step in the Vin Santo production, because of the risk of increasing the incorporation of suspended solids that decrease juice quality. Despite this, vertical or horizontal presses are still used as they can help to extract the greatest possible... 

Another predominant furan, namely furfural, is described as sweet and bread-like caramellic. This furan can interact with hydrogen sulfide of juice to produce thiofurfural, a compound with a skunky odor (35). Furfural has an important role in the monitoring of citrus juice quality (36), and has an especially significant relationship to browning (34). The main source of furfural in aged citrus products is by oxidative degradation of ascorbic acid. Furans, such as deoxyfuroin, furoin and furil are probably formed by self-condensation of furfural (37). 

Godshall, M. A., Legendre, B. L., Richard, C., and Triche, R., Effect of Harvest System on Cane Juice Quality, Proc. Sugar Processing Research Conf, 222-236, 2002. 

The rack and frame press is a further development of the basket press. Rack and frame presses are commonly used on farms that process apples and pears. They are particularly suitable for mashes that are difficult to press. They give high yields and good juice quality with little suspended... 

---