Technical note: Effect of low pH preservation on the colour and consistency of tomato juice

Abstract

The changes in colour and consistency are reported for tomato juice produced by low pH preservation and stored under ambient conditions. The juice preserved under acid conditions showed higher consistency, probably due to the higher concentration of pectin and the presence of low methoxyl pectin. The furfural and hydroxymethylfurfural which were detected in the juice indicated that darkening of the juice colour was due to non-enzymic browning involving both ascorbic acid and sugars (hexoses). Although the retention of ascorbic acid was higher under low pH conditions, it led to a significant darkening of the juice colour due to non-enzymic browning involving mainly ascorbic acid.

Proximate, Mineral and Vitamin Content of Flesh, Blanched and Dried Tomatoes (Lycopersicon esculentum)

“…These results are consistent with studies on blanching which show the highest average losses of vitamin C for tomatoes, spinach, broccoli and relatively lower amounts for legumes [25]. Studies have shown that destruction of ascorbic acid is directly related with temperature and air [26,27]. Some researches support the common perception that fresh vegetables are often best for optimal vitamin C content, as long as the fresh product undergoes minimal storage at either room or refrigerated temperatures [27].…”

“…Studies have shown that destruction of ascorbic acid is directly related with temperature and air [26,27]. Some researches support the common perception that fresh vegetables are often best for optimal vitamin C content, as long as the fresh product undergoes minimal storage at either room or refrigerated temperatures [27]. Blanching and drying process is not as destructive to ascorbic acid, but continued storage and subsequent cooking of fruit and vegetable products result in significant degradation of the vitamins [28].…”

Comparison of Solid-Liquid Separation (SLS) and Vacuum Concentration of Tomato Juice

“…Hue angle in the final samples decreased as the insoluble solids increased during concentration in vacuum concentration, except the color of commercial samples (Fig. The color change from vacuum concentration is likely caused by browning due to the Milliard reaction and degradation of ascorbic acid, which occurs during thermal treatments (Mudahar et al 1986;Eichner et al 1996). The color change from vacuum concentration is likely caused by browning due to the Milliard reaction and degradation of ascorbic acid, which occurs during thermal treatments (Mudahar et al 1986;Eichner et al 1996).…”

“…5). The color change from vacuum concentration is likely caused by browning due to the Milliard reaction and degradation of ascorbic acid, which occurs during thermal treatments (Mudahar et al 1986;Eichner et al 1996). The commercial samples had already been retorted, so further mild heat treatment would not greatly affect the color.…”