Writing in the journal Food Research International, Paula Leona and Ana Rojas from Universidad de Buenos Aires report that the stability and non-enzymic browning (NEB) of vitamin C were reduced by incorporation in the gellan film.
"An edible film based on gellan polymer was elaborated as a first approach for carrying ascorbic acid (AA) on films with nutritional purposes and as food antioxidant. It was found that AA was 100 per cent-retained after film casting," wrote the authors.
Gellan is seeing increasing demand and use in food formulation due to its thermal stability and relative resistance to acid medium. In addition to its high efficiency as a gelling agent the gum is said to have a "sparkling clarity".
Leona and Rojas prepared the films by dissolving gellan (one per cent, CP Kelco) in water. Glycerol was added to act as a plasticizer. The retention of vitamin C (l-(+)-ascorbic acid) was tested at different humidity levels (33.3, 54.7 or 75.2 per cent).
They report that the initial retention of the vitamin was 100 per cent, with half lives (time taken for vitamin levels to decrease by 50 per cent) decreased with increasing humidity levels - 36, 26 and 11 days for 33.3, 54.7 or 75.2-relative humidity levels, respectively.
"An edible gellan film for carrying AA was developed with the objective of its future application for enhancing food nutritional quality and for developing an antioxidant action, by leveraging its barrier properties to gases and antioxidant activity," wrote the researchers.
"Taking all these facts into account, it was suggested that ascorbic acid degradation and NEB can be better controlled through an adequate selection of the hydrophilic polymer used for edible film constitution, when biopolymers are used," they concluded.
Interest is growing in natural food additives as replacements to synthetic antioxidants like butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT) to slow down the oxidative deterioration of food.
Indeed, according to a 2003 report by Frost and Sullivan, the synthetic antioxidant market is in decline, while natural antioxidants, such as herb extracts (particularly rosemary), tocopherols (vitamin E) and ascorbates (vitamin C) are growing, pushed by easier consumer acceptance and legal requirements for market access.
Source: Food Research International (Elsevier)
June 2007, Volume 40, Issue 5, Pages 565-575
"Gellan gum films as carriers of l-(+)-ascorbic acid "
Authors: Paula G. Leona and Ana M. Rojas