Compositional analysis of locally cultivated carob (Ceratonia siliqua) cultivars and development of nutritional food products for a range of market sectors

[摘要] Carob (Ceratonia silliqua) is an evergreen, drought resistant tree of Mediterranean origin.Popularly known as St John's bread, the carob pod has a long history of use in food (over4 000 years). Carob has a good nutritional value, a long shelf-life (2-3 years) and it isrelatively cheap. Due to its high sugar content, carob is naturally sweet. It also has anutty chocolate-like flavour, but unlike chocolate or cocoa, carob does not contain anycaffeine, thiobromine or oxalic acid. In addition, carob is normally regarded as a healthyfood because of its low fat content (0.2 – 2.3%). Carob trees are also found in SouthAfrica, especially in the Western Cape Province. Locally, carob trees have been usedmainly ornamentally or as a source of animal fodder, with minimal use of the pods as anutritious food source. Knowledge of the nutritional composition and the overall nutritionalpotential of locally (South African) grown carob cultivars is also limited. Carob couldpotentially be used as an alternative food source in South Africa as currently, most of thisnutritious product goes to waste each year.In this study, the feasibility of using carob pods as an alternative source of food inSouth Africa was investigated. This was done by firstly, analysing the cultivars forproximate composition (moisture, carbohydrates, sugars, dietary fibre, protein,polyphenols, fat and ash) as well as for amino acids, fatty acids and minerals, in order todetermine and compare their nutritional contents. Five cultivars (Tylliria, SFax,Aaronsohn, Santa Fe and an 'Unknown cultivar) were examined. The average proximatecomposition of raw carob pods was 8.17 – 9.56% moisture, 89.57 – 91.12% carbohydrates,40.69 – 54.74% total sugars (33.70 – 45.09% sucrose, 1.79 – 4.95% glucose and 1.80 –5.19% fructose), 29.88 – 36.07% dietary fibre, 3.07 – 4.42% protein, 2.58 – 3.08%polyphenols, 0.45 – 0.86% fat and 2.13 – 2.69% ash. Seven essential amino acids werepresent in all the cultivars, except for methionine which was not detected in the Singleunknown cultivar. This study has shown that all the cultivars had good long-chain fattyacid (LCFA) proportions in terms of the saturated to polyunsaturated fatty acid (SFA:PUFA) and n-6 to n-3 ratios. The short-chain fatty acid content of the cultivars was low.All nine minerals (calcium, phosphorus, potassium, magnesium, sodium, manganese, iron,copper and zinc) analysed for in this study were detected in all five carob cultivars and allcultivars were very low in sodium.The impact of various roasting times (45, 60 and 75 min) at 150ºC, on thetemperature sensitive components such as sugars, protein and fat, was also examined.Roasting had no significant (P>0.05) effect on the fat content. Although roasting significantly (P<0.05) reduced the sugar and protein content from 54.74 to 32.53% and3.59 to 3.18%, respectively, levels in both raw and roasted carob still represented apotentially nutritious food source and alternative to cocoa.A variety of food products targeted at the various food market sectors weredeveloped with carob as an ingredient. The formulations for five new food products(bread, porridge, breakfast cereal, mousse and milk-based drink) were developed wherecarob had successfully been incorporated as an ingredient. Microbiological and consumersensory analyses carried out showed that all products developed were safe andacceptable. The findings of this study provide useful scientific evidence towards the factthat carob could potentially be used as an alternative food source in South Africa.

[发布机构] Stellenbosch University