Biological resource development and utilization

Author: Yi Meihua (Editor) / Country:
Publisher:
Publishing Time: 2003-06-01
Features: [Excerpt:] Bran contains rich proteins, lipids, vitamins, and minerals, as well as many harmful substances such as enzymes, microorganisms, insects, and natural toxic components. Therefore, the quality of bran is prone to deterioration. Before utilizing bran, the issue of its quality stability must be addressed first. There are many factors that affect the deterioration of bran quality, mainly insects, microorganisms, and enzymes in bran, such as lipase and oxidase. For whole brown rice, lipolytic enzymes are located in the pericarp, while lipids are in the aleurone layer, subaleurone layer, and embryo. Due to their different locations, they do not react. Once the rice is milled, the enzymes mix into the bran, and hydrolysis occurs immediately, rapidly hydrolyzing free fatty acids. Under the action of enzymes such as oxidase, bran undergoes acidification. Economically and effectively inactivating and inhibiting the activity of bran lipase can stabilize the quality of bran and delay spoilage. The main methods for inactivating and inhibiting bran lipase activity include freezing, chemical treatment, radiation, and heat treatment. From an economic and technical feasibility perspective, heat treatment is widely adopted.
China has a wide variety of fruits and vegetables, extensive cultivation areas, and high yields. During the harvest season each year, in addition to supplying large quantities of fresh fruits and vegetables and processed products for storage, there are often significant amounts of by-products such as fruit fragments, peels, cores, seeds, and other waste materials from fruit and vegetable processing. Additionally, during the entire production process from cultivation to harvest, there are also large quantities of fallen flowers, fallen fruits, and substandard fruits. However, these waste materials contain many useful components. According to incomplete statistics, in fruit and vegetable juice production, by-products account for the weight of processed raw materials as follows: apples 20%–40%, pineapples 50%–60%, citrus 50%–55%, grapes 30%–32%, passion fruit 50%–66%, bananas 30%, tomatoes 10%, carrots 30%–50%, chili peppers 24%, green peas 60%, and asparagus 80%. Such a large volume of by-products will become a valuable resource for the food industry. The comprehensive utilization of fruits and vegetables, primarily focused on fruits, allows not only for the production of fruit juice beverages, canned products, fruit wine, and fruit vinegar but also for the creation of valuable products from by-products, which can be applied in the food, pharmaceutical, and chemical industries.
### I. Classification of Fruit and Vegetable Juices
Fruit and vegetable juices generally refer to natural juices and artificially prepared fruit and vegetable beverage drinks, which are entirely different in composition and nutritional effects. The former are nutritious health foods, while the latter are purely indulgent beverages and are not within the scope of this section. Below are several common types of fruit and vegetable juices.
#### (1) Original Fruit and Vegetable Juices
Original fruit and vegetable juices, also known as natural fruit and vegetable juices, are juices (or nectar) directly extracted from fresh fruits and vegetables. Original fruit and vegetable juices can be divided into clarified fruit and vegetable juices and cloudy fruit and vegetable juices.
1. Clarified Fruit and Vegetable Juices
Clarified fruit and vegetable juices are also referred to as transparent fruit and vegetable juices. Examples include general grape juice and apple juice. Due to the removal of some tissue particles and pectin, these juices have high stability, but their flavor, color, and nutritional value are also compromised. Therefore, most countries advocate the production of cloudy fruit and vegetable juices.
2. Cloudy Fruit and Vegetable Juices
Cloudy fruit and vegetable juices have a uniform, cloudy liquid appearance and contain suspended particles. Their manufacturing process differs from that of clarified juices, as they are not clarified but must undergo high-pressure homogenization. Large particles are not allowed to ensure commercial value. Most of the nutritional components in these juices are present in the suspended particles, making them richer in flavor, color, and nutritional value compared to clarified juices.
#### (2) Concentrated Fruit and Vegetable Juices (Pulps)
Original fruit and vegetable juices (pulps) are concentrated to a solids content of 20°Bé or higher through evaporation, freezing, or other appropriate methods. These juices must not contain additives such as sugar, colorants, preservatives, flavorings, emulsifiers, or artificial sweeteners. Concentration ratios range from 3 to 6, with soluble solids content as high as 60%–75%. Currently, concentrated fruit and vegetable juices account for about 20% of fruit and vegetable beverages in China. The raw materials for concentrated fruit and vegetable juices (pulps) in China include apples, oranges, citrus, blackcurrants, pineapples, passion fruit, grapes, sea buckthorn, carrots, peaches, apricots, strawberries, mangoes, and hawthorns.
#### (3) Fruit Syrup (Sweetened Juice, Juice Syrup)
Fruit syrup is a product prepared by adding a large amount of edible sugar to original juice or by mixing a certain proportion of juice into syrup. It is generally high in sugar but can also be high in acidity. Typically, it has a soluble solids content of 45% or 60%.
#### (4) Fruit Juice Powder
Fruit juice powder is a dehydrated dry product made by spray drying from concentrated fruit juice or fruit syrup, with a moisture content of 1%–3%. Common products include orange juice powder.
The varieties of fruit and vegetable juice beverages in China have initially formed a structure dominated by orange juice and apple juice, with strawberries, peaches, apricots, hawthorns, and grapefruits as secondary options. Especially in recent years, the rise of mixed fruit and vegetable juice beverages, high-fiber fruit and vegetable beverages, and fruit juice milk has pushed the fruit and vegetable juice beverage market to new heights. The development of fruit and vegetable juice production has been extremely rapid, with new products constantly being developed. Therefore, to date, there is no perfect classification method for fruit and vegetable juices. Refer to GB 10789—1996.
### II. Processing Technology of Fruit and Vegetable Juices
#### (1) Raw Material Selection and Washing
The raw materials for fruit and vegetable juices must have rich juice content, easy extraction, high juice yield, good flavor, stable color, appropriate acidity, and maintain these excellent qualities without significant adverse changes during processing. Freshness and ripeness, free from mold, pests, and diseases, are important measures to ensure juice quality. Before juicing, raw materials should be thoroughly washed to remove dust, pesticides, and some microorganisms from their surfaces. For raw materials pressed with skins, special attention should be paid to the cleanliness of the washing water, avoiding repeated recirculation. When necessary, non-toxic surfactants can be used for washing, or disinfectants such as sodium hypochlorite, potassium permanganate, or hydrogen peroxide may be used.
#### (2) Raw Material Crushing and Pressing or Extraction
Except for berry fruits, most raw materials need to be crushed before juicing or extraction. Crushing increases juice yield, but the degree of crushing should be appropriate. If the fruit pieces are too fine, the juice may not flow out easily during pressing. Generally, the particle size of the fruit pulp should be between 3 and 9 mm. To improve juice yield, heating treatment can be added after crushing, such as 40–50°C for 5–6 hours or 60–70°C for 15–30 minutes. For raw materials rich in pectin, such as kiwifruit, bananas, and carrots, a suitable amount of pectinase should be added to reduce the viscosity of the juice, facilitate filtration during pressing, and improve juice yield. Crushing can be done using a crusher or a slicer, with the crushing time kept as short as possible to avoid oxidation and discoloration. The juice that flows out from the crushed fruit before pressing is called "self-flow juice," while the juice that flows out after pressing is called "pressed juice." Self-flow juice is clearer and has a more refreshing color than pressed juice. Commonly used presses include screw presses, lever presses, conical presses, and controlled presses. Regardless of the type of press used, the fruit residue is usually stirred and pressed a second time after the first pressing. In some cases, a small amount of hot water is added to the fruit residue, soaked for 6–8 hours, and then pressed a second time. This can improve juice yield. The juice yield of fruits varies, with berries being the highest, citrus and pome fruits being slightly lower. Strawberries have a juice yield of 60%–75%, grapes 65%–80%, apples and pears 55%–70%, and wide-leaved oranges 35%–40%. For raw materials with lower juice content, water extraction can be used. For example, to extract juice from hawthorns, the hawthorns can be pitted, decapitated, crushed, and then extracted with warm water.
#### (3) Coarse Filtration (Screening)
Freshly pressed fruit and vegetable juices often contain large suspended particles, such as stalks, seeds, and other impurities, which should be filtered promptly. Filtration includes coarse filtration and fine filtration. Coarse filtration removes large suspended particles, which is suitable for cloudy juices and beneficial for preserving the color, flavor, and nutritional value of the juice. Fine filtration is suitable for clear juices but may filter out some nutritional components. In production, coarse filtration can be arranged during the juicing process. Typically, a fine mesh screen is installed at the outlet of the press to allow the juice to pass slowly. Coarse filtration can also be performed separately after juicing.
Note: The section titled "Roasted Laver" seems to be unrelated to the main content and appears to be incomplete. It may be a separate topic or a continuation of a different section.