Gmp Gmp Gmp

500 mg/kg GMP

GMP = good manufacturing practices. Source: Adapted from JECFA (2001).49

legislation, grape commercial extracts are used mainly for beverages, soft drinks, as well as confectionery products (Table 8.11).3-40-48-49

In addition, the food industry is demanding a natural pigment that effectively substitutes for FD&C red No. 40, the certified dye with highest per capita consumption in the United States; in this sense, red radish extract has similar coloring characteristics with the synthetic colorant. In addition, the anthocyanins of red radish have good stability; maraschino cherries colored with radish anthocyanins have a shelf life of at least 6 months at 25°C, and their stability has been associated with the presence of acylated pelargonidin derivatives. The proposed method to produce radish anthocyanins uses an abrasive peeler that is followed by pressing of the epidermal pulp; this strategy produces recoveries greater than 90%. In this process, it is not necessary to use macerating or depectinizing enzymes; blanching and refrigeration are adequate to clarify the juice, which is concentrated using a Cen-tritherm evaporator followed by a direct osmosis concentration (MWCO = 500). The use of this combined strategy produces a 10.7-fold concentrate in ~4 h, resulting in a juice with high anthocyanin content (400 mg/100 ml at 16° Brix) and low aroma.50

8. Processing and Stability a. In Model Systems

Anthocyanins are pigments common in vegetables and fruits; their appearance in fruits and fruit products in particular give them a great economic importance. As is well known, a good appearance is essential to achieve good market prices.1 In addition, industry is demanding natural pigments, especially natural red colors, and anthocyanins are candidates for the introduction of these tone colorants. The main drawback, as with other natural pigments, is instability; indeed, researchers and processors look continuously for anthocyanin preparations with high stability. Their color is associated with the presence of multiple double bonds in their structure; however, the structure in resonance is the cause of their instability. Additionally, and

Acidic conditions

FIGURE 8.4 Structural transformations of anthocyanins by effect of changes in pH. Rx could be H, OH, or OCH3 depending on the considered pigment. It is common to observe, in nature, glycosidic groups in the R1, R2, and R4 groups. In addition, acyl groups are commonly attached to the glycosidic residues.

Acidic conditions

FIGURE 8.4 Structural transformations of anthocyanins by effect of changes in pH. Rx could be H, OH, or OCH3 depending on the considered pigment. It is common to observe, in nature, glycosidic groups in the R1, R2, and R4 groups. In addition, acyl groups are commonly attached to the glycosidic residues.

as a direct consequence, the groups attached to the structure, such as hydroxyl, methoxyl, glycosyl, and acyl, influence the stability. In fact, diglucosides are more stable than monoglucosides but browning reactions are favored for diglucosides as a consequence of an additional sugar molecule. Another rule is that a hydroxyl group in the 4-position is associated with redder tones.3

Anthocyanin colors are highly affected by pH and, in solution, they are in equilibrium of colored (cationic)-uncolored (pseudobase) structures. The cationic form (flavilium ion) is favored at low pH values and equilibrium is displaced toward the uncolored forms as the pH goes toward neutral values (Figure 8.4). Moreover, when hydroxyl groups are present at the 7- or 3'-positions, quinonoidal equilibrium is favored as the pH is increased, but in contrast to the pseudobase-uncolored structures, the quinonoidal structures are colored with tones going toward blue (Figure 8.5). As can be deduced, flavilium cation appears at low pH values and at higher pH values a mixture of pseudobase and quinonoidal structures are observed. Some anthocyanins are red in acid solutions, violet or purple in neutral solutions, and blue in alkaline pH. Based on these characteristics, it is easy to understand why anthocyanins are commonly used at pH values below 4 (Table 8.12).1740 Interestingly, it has been found that certain anthocyanin 3-glucosides (e.g., malvidin-3-glucoside) show a relatively high stability in the alkaline region; thus, these pigments are suggested as potential colorants for some slightly alkaline products.

The stability of some fruit anthocyanins has been evaluated at pH values in the range 1 to 12; these compounds are pelargonidin 3-glucoside (strawberry), cyanidin 3-glucoside and peonidin 3-glucoside (Abies koreana), and malvidin 3-glucoside (blueberries), among others. They are classified into two groups: group I consists of the pelargonidin, peonidin, and malvidin 3-glucoside, whereas in group II are cyanidin, delphynidin, and petunidin 3-glucosides. The anthocyanins of group I show parallel curves associated with a bathochromic change up to pH 6.0. A sharp increase is observed in the range 6 to 7.6 and it is no longer observed above pH 8.0; the

FIGURE 8.5 Structural transformations of anthocyanins by effect of changes in pH. Rx could be H, OH, or OCH3 depending on the considered pigment. It is common to observe, in nature, glycosidic groups in the R1 and R2 groups. In addition, acyl groups are commonly attached to the glycosidic residues. When free hydroxyl groups are in the positions corresponding to R4 or R6, increases in pH induce formation of quinoid bases.

FIGURE 8.5 Structural transformations of anthocyanins by effect of changes in pH. Rx could be H, OH, or OCH3 depending on the considered pigment. It is common to observe, in nature, glycosidic groups in the R1 and R2 groups. In addition, acyl groups are commonly attached to the glycosidic residues. When free hydroxyl groups are in the positions corresponding to R4 or R6, increases in pH induce formation of quinoid bases.

Was this article helpful?

0 0

Post a comment