Optimization of reduced calorie tropical mixed fruits jam

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Abstract

Response surface methodology using mixture design was used to determine the optimum ratio of pineapple, papaya and carambola in the formulation of reduced calorie tropical mixed fruit jam. Ten formulations covering the entire range of a triangular simplex were subjected to sensory evaluation. Contour plot of sensory attributes showed that formulations containing 3.5–37.7% papaya, 0–15% carambola and 61.5–96.5% pineapple produced optimum acceptance. A predicted optimum formulation containing 71% pineapple, 25% papaya and 4% carambola together with two non-optimal formulations were selected and subjected to sensory evaluation to confirm the validity of the model. There was a significant difference (P⩽0.05) between the predicted optimum and the other two tested formulations. Results obtained matched the predicted value where the optimum formulation received the best sensory scores for most attributes tested. The optimum mixed fruit jam formulation contained 106 kcal/100g which is one-third of the caloric value of a normal jam.

Introduction

Technology plays an important, dynamic role in consumer food choices and their ability to achieve dietary goals. Consumers are increasingly better informed about diet, and health, and as a result, desire more foods which offer, in addition to convenience, high quality, safety, optimum nutrient balance, less fat/cholesterol/sugar and fewer calories. At the same time foods must remain tasty and at an economical price. Technological innovations in agriculture, food processing, formulation, packaging, and distribution integrated with traditional production and processing methods, enable innovative food processors to meet these demands with foods which fit into changing habits. A record number of new food products are introduced in the USA annually (Anon, 1988). Of 7866 new products introduced in 1987, 432 featured low or reduced calories or other dietary claims. For the past decade, production of low calorie food has expanded and is considered a multi-billion dollar industry. In the UK, sales of low/reduced calories amounted to more than $800 million with estimated growth of 5% per year (Hendley & Seymour, 1987) whereas in the USA the sales reached 40 billion dollars in 1990. Among reduced or low calories food available in the market are jam, jelly and spread.

In 1990 Malaysia exported RM830,000 worth of jam and jelly and imported RM1,858,700 jam and jelly. Most of the jam processed in Malaysia uses imported fruits such as strawberry, gooseberry, blackcurrant and grape. The tropical fruit most widely used by local processors is pineapple. Other local tropical fruits used are papaya, banana, mango, carambola guava and rosselle. These fruits are used either singly or in combination. According to the Food Act (1983) and Food Regulations Malaysia (1985):

  • 1.

    Jam shall be the product prepared by boiling one or more types of sound fruits, whether raw, processed or semi-processed, with a permitted sweetening substance with or without added pectin.

    • (a) For the purpose of this regulations, ginger shall be deemed to be fruits.

  • 2.

    Jam shall contain not less than

    • (a) 35% fruit except that passion fruit jam and ginger jam may contain not less than 6% and 5% of fruit respectively, and

    • (b) 65% of soluble solids determined by refractometry at 20°C, i.e. uncorrected for insoluble solids.

  • 3.

    Jam may contain permitted preservatives, permitted colouring substance: permitted flavouring substance and permitted food conditioner.

  • 4.

    There shall be written on the label on a package containing jam made up of more than one type of fruits the words ‘mixed fruit jam’.

Reduced calorie is a nutritionally altered product that contains 25% less of nutrient or 25% fewer calories than a reference food. Since there are not many reduced calorie tropical mixed fruit jams available in the market, an experiment was conducted to formulate and optimize the use of three different types of tropical fruits, namely pineapple, papaya and carambola in reduced calorie jam.

Section snippets

Samples

Pineapple, papaya and carambola were obtained from the local market and allowed to ripen at ambient temperature. Papaya (Carica papaya) var. Subang, Carambola (Averrhoa carambola L) cv B10 and pineapple (Ananas comosus) cv Mauritius all at ripening index of 4 were peeled, blended and mixed accordingly to the 10 formulations using a mixture design. The maturity index of papaya, carambola and pineapple were based on Rashidah (1989), Lam and Abdullah, 1984, Zainun, 1992, respectively. Using a

Result and discussion

Mean sensory scores for various attributes of 10 jam formulations are shown in Table 2. There were significant differences (P⩽0.05) in all sensory attributes evaluated, except for spreadibility. In terms of overall acceptability, there was no significant difference among jam formulated using 100% pineapple, combination of pineapple and papaya (50:50) and mixture of pineapple, papaya and carambola (75:12.5:12.5). However, the addition of papaya significantly improved the colour of jam.

The

Acknowledgements

The authors wish to acknowledge IRPA (1-07-03-06) for funding the research. The services provided by Mohd. Nor Hayati, Mr. Mohd. Din and Mr. Ain Ali in the preparation of this manuscript are highly appreciated.

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