Process for preparing beverage containing β-carotene
BACKGROUND OF THE INVENTION 
     The present invention relates to a process for preparing a β-carotene fortified beverage in order to prevent the loss of β-carotene, more particularly by the admixture of vitamins C, B 2  and E with β-carotene to stabilize the latter even in ambient conditions to minimize its loss in the form of a beverage; in addition, the admixture of such anti-oxidative vitamins is designed in a well-balanced fashion for human nutrition. 
     β-carotene, now regarded as one of the primary functional components, has been considered to be provitamin A. However, recently its anti-oxidative property has drawn keen attention. Namely, β-carotene has been found to neutralize singlet oxygen which otherwise primes preoxidation of unsaturated fatty compounds. The reactive oxygen is generated from inspired oxygen and results in pathological aging with excess oxidative stress. The effective modulation of reactive oxygen may mean anti-aging. Therefore, there would be no surprise even though the constant intake of β-carotene has been shown to decrease the incidence of cancer, especially lung cancer, in epidemiological research. A lower content of serum β-carotene in a smoker might be due to ample free-radicals in the puffed fume. Therefore, intake of enough B-carotene constitutes a good preventive measure for the most serious kinds of cancer. Thus, it has long been sought to provide any easily accessible source of β-carotene in daily life. 
     A known beverage containing β-carotene includes carrot juice, as well as the mixture of carrot juice with other juice or juices, with or without fortification of its principal components, and is sold in can, bottle, carton, or plastic container. Even short surveys of this kind of product disclose very poor shelf-life, namely degrading color, flavor and taste over time. Especially, β-carotene is prone to discolor or oxidize by the irradiation of light (C.A. Pesek and J. J. Warthesen, J. Food Science 52 (3), 1987). Naturally, β-carotene is not only photo-sensitive but also reactive with oxygen, reflected by its structure, which makes construction of a long-life beverage containing β-carotene a matter of difficulty. 
     It is no wonder that so far no effective protection method has been invented for preparing such a β-carotene beverage. We extensively pursued the above aim, namely, how to stabilize the β-carotene moiety in a long-life beverage under ambient conditions without vitiating its flavor and have thus completed the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a method of preparing a beverage containing β-carotene by coexisting three other anti-oxidative vitamins, namely vitamins C, B 2  and E, in order to prevent the loss of β-carotene; and a method of preparing a beverage containing β-carotene, in an amount of 3-20 mg per 100g of beverage, by coexisting vitamins C, 60-120 mg, E, 5-10 mg, and B 2 , 0.5-1.0 mg, each amount per 100 g beverage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1-1 shows the change in β-carotene content of a beverage Specimen No. 1 solely fortified with β-carotene. 
     FIG. 1-2 shows the change in β-carotene content of a beverage Specimen No. 1 solely fortified with β-carotene and stored up to 6 months. 
     FIG. 2 shows the change in β-carotene content of a beverage Specimen No. 2 fortified with both β-carotene and vitamin C. 
     FIG. 3 shows the change in β-carotene content of a beverage Specimen No. 3 fortified with both β-carotene and vitamin E. 
     FIG. 4-1 shows the change in β-carotene content of a beverage Specimen No. 4 fortified with β-carotene and vitamins C and E as well as B 2 . 
     FIG. 4-2 shows the change in β-carotene content of a beverage Specimen No. 4 fortified with β-carotene and vitamins C and E as well as B 2  and stored up to 6 months. 
     Specimens No. 1 to No. 4 were prepared as described in Example below. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present invention, β-carotene may be derived from plants, carrots and green algae, by being crushed, squeezed, extracted and condensed into a puree or paste form, or chemically synthesized into a natural form from appropriate starting material. Other vitamins are procured from ordinary commercial sources. 
     In the present invention, the relative composition of the vitamins to supplement the beverage should be at least in the following range (per 100 g of beverage): 
     β-carotene: 3 to 20 mg 
     vitamin C: 60 to 120 mg 
     vitamin E: 2 to 10 mg 
     vitamin B 2  : 0.3 to 1.2 mg 
     The effects of the present invention are as follows: 
     1) In the presence of vitamin E, β-carotene can stay intact at the expense of vitamin E oxidation; 
     2) Then, oxidized vitamin E can be reduced by the vitamin C present and completely recycled for the protection of β-carotene; and 
     3) Vitamin B 2  can protect β-carotene from the irradiation of light with coexisting vitamin C by dispensing photons in the system. 
     EXAMPLE 1 
     The preparation of a β-carotene beverage was performed by the following steps: 
     
         ______________________________________                                    
Raw materials (Basal mixture plus vitamins)                               
______________________________________                                    
Stirring to form a mixture                                                
↓                                                                  
Preheating and degassing                                                  
↓                                                                  
Homogenization                                                            
↓                                                                  
Sterilization &amp; cooling                                                   
↓                                                                  
Aseptic filling into container                                            
______________________________________                                    
Composition of basal mixture                                              
Ingredients  Percentage (by weight)                                       
______________________________________                                    
Carrot juice 75                                                           
Apple juice  20                                                           
Lemon juice   3                                                           
Honey         2                                                           
______________________________________                                    
 
    
     β-carotene to fortify as well as vitamins E, C and B 2  were added to the basal mixture stepwise to organize the following specimens No. 1-4 in aseptically filled brick packs (paper cartons). The vitamins were traced as to their contents after 4 weeks at 35° C. and 6 months at 10° and room temperature. 
     Specimen No. 1: Basal mixture plus β-carotene to fortify 
     Specimen No. 2: No. 1 plus vitamin C 
     Specimen No. 3: No. 1 plus vitamin E 
     Specimen No. 4: No. 1 plus vitamin C, E &amp; B 2   
     As shown in FIGS. 1-1 to 4-2, β-carotene stays reasonably intact in the presence of protective vitamins. 
     EXAMPLE 2 
     Specimen No. 5 was prepared as described above except for the addition of β-carotene with (No. 5-2) or without (No. 5-1) vitamins B 2  and C to the basal mixture and aseptically packed in a transparent glass bottle. The bottle was exposed to the irradiation of a fluorescent lamp (30W) for 2 weeks at room temperature. Table 1 shows changes in β-carotene and the coexisting vitamins, before and after 2 weeks of irradiation. The vitamin content was expressed in relative intensity with 100 signifying &#34;before irradiation&#34;. Table 1 clearly shows the protective effect of vitamins C and B 2  for β-carotene under the irradiation of a fluorescent lamp. 
     
                       TABLE 1                                                     
______________________________________                                    
Changes in β-carotene content under irradiation                      
with coexisting vitamins B.sub.2 and C                                    
Specimen                                                                  
       Irradiation                                                        
                  β-carotene                                         
                            vitamin B.sub.2                               
                                    vitamin C                             
______________________________________                                    
No. 5-1                                                                   
       Before     100    (%)  /       /                                   
       After      63          /       /                                   
No. 5-2                                                                   
       Before     100         100     100                                 
       After      91           51      10                                 
______________________________________                                    
 
    
     The present invention makes possible a handsome intake of β-carotene, which is a necessary nutrient in modern life, without significant loss in storage and with a well-balanced assortment of anti-oxidative vitamins C, E and B2.