Betalains stability

Since several previous reviews have treated betalain stability, the interested reader is referred to those for more detailed information. "" " " This chapter is intended to present some general aspects of handling betalainic foodstuffs. 

Most published data deals with model solutions to assess the major factors influencing betalain stability, among which pH and temperature are most frequently addressed. Until recently, total color loss was assessed by spectrophotometric monitoring of the decline at the wavelength of maximum absorption. To predict color fading over time, kinetic data were derived therefrom, most often obeying first-order decay principles. 

It should also be kept in mind that the pigment solution under investigation should exhibit a constant pH. Mcllvaine buffer was found to be the most suitable because it contains both citric acid and phosphate ions previously reported to enhance betalain stability. According to our observations, a pH of 6.0 or 6.5 should be chosen for spectrophotometric quantification, and not more than 20% of the final dilution should stem from the sample. 

Delgado-Vargas, R, Jimenez, A.R., and Paredes-Lopez O., Natural pigments carotenoids, anthocyanins, and betalains — characteristics, biosynthesis, processing, and stability, Crit. Rev. Food Sci. Nutr., 40, 173, 2000. 

Betalains are vacuolar plant pigments. Hence their hydrophilic nature is comprehensible. Although they are slightly soluble in ethanol and methanol, water is the best snited solvent both for stability and solnbility reasons. In contrast to the antho-cyanins, the betalains are even more polar as can be demonstrated by shorter retention times in RP-HPLC and lower solubilities in alcoholic solutions. The varying polarities may also be beneficially used to separate anthocyanins from betalains on an RP-18 solid-phase extraction cartridge (Stintzing, unpublished data). 

Von Elbe, J.H., Stability of betalaines as food colors, Food TechnoL, 29, 42, 1975. Kimler, L. et al., Betalamic acid, a new naturally occurring pigment, J. Chem. Soc./Chem. Commun., 21, 1329, 1971. 

Mosshammer, M.R. et al.. Stability of yellow-orange cactns pear (Opuntiaficus-indica [L.] Mill. cv. Gialla ) betalains as affected by the jnice matrix and selected food additives. Fur. Food Res. TechnoL, 225, 21, 2007. 

Vareltzis, K.R and Buck, E.M., Color stability and sensory attributes of chicken frankfurters made with betalains and potassium sorbate versus sodium nitrite, J. Food Protect., 47, 41, 1984. 

Betalains in Food Occurrence, Stability, and Postharvest Modifications... 

As soon as betalains are extracted from the vacuoles through plant tissue decom-partmentalization, they are prone to degradation. Factors supporting stabilization or rather destabilization are summarized in Figure 4.4.2. 

From a technological view, measures to stabilize betalains during the production process need to be elaborated. Some approaches have been described in the earlier literature, mainly for red beets and only recently for alternative crops such as cactus... 

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