Fruit By-Products utilization in extruded breakfast snacks and cereals


N Sai Prasanna¹, Anil Kumar K²

Most of the food by-product wastes all around the world are generated in fruit, vegetable, wine and beer processing industries and also along the food supply chains. Fruit by products like peels or outer skin, rinds and seeds are generally discarded during the consumption or manufacturing stage of fruit industry. In recent times, fruit pomace has been recognized as a functional ingredient and source of dietary fibre in developing new food products. Fruit pomace is the solid matter that remains after juice extraction of fruits and might include seeds, skin, pulps, and stems from certain fruits. The by-products developed from fruit processing industries are rich in bioactive compounds like phenolics, carotenoids, powerful anti-oxidants, polyunsaturated fatty acids, vitamins and pigments that provide potential nutritional value and nutraceutical functionality for developing novel, new and sustainable functional food products. 

One of the most important applications of these by-product fruit pomace powders are directly expanded cereal-based snack products. These extruded snack products are popularly consumed by all age group people from elder to babies. Extrusion is the most promising and contemporary processing technology in food industry that provides inexpensive supplementary snack foods and cereal-based expanded products like breakfast cereals. Extrusion is a continuous process that consists of mixing, shearing, heating, cooking and shaping of feed material. This technology provides high quality products at low cost with no effluents and possibility of product design. Extruded cereal based snack products formed at high temperatures and low moisture contents renders nutritional and bioactive compounds losses in final extruded products, and also forms variety of Maillard's reaction in products with potential harmful effects (Lohani et al., 2017). Since present snack market is dominated with instant snacks and ready to eat cereal food products mainly composed of rice, corn and oats flour that are high in carbohydrates, fats and salts, and low in essential nutritients and minerals². Therefore, these cereal extruded snacks are required to be fortified with fruit based by-products at present times as an alternative to improve its nutritional quality without compromising its shape, texture and colour.

Extruded breakfast cereals and snacks made out of cereal ingredients, i.e., barely flour, rice flour, oat flour, pulse flours, wheat bran, corn grits or meal, oat bran, potato starch, corn starch, sorghum include fraction of fruit pomace and other by products from various fruits like grape pomace, black currant seeds or pomace, blueberry pomace, cranberry pomace, bilberry extract, orange peel, grape seeds, tomato pomace³, chokeberry pomace4, carrot pomace5, cashew apple pomace6, apple pomace², olive pomace7, naranjita pomace8, pineapple pomace? as a functional ingredient for dietary fibre and Polyphenol enrichment in extruded snacks and cereal foods.

Effect of fruit by-products on the extrusion parameters 

The physical quality properties that influence the extruded breakfast cereals are density, texture, colour and water solubility index. 

  • Colour of the extrudates intensified with increase in amount of fruit by-products. Degradation of pigments in by-products, maillard reactions and oxidation during extrusion process causes this colour change.
  • Extrudates are formed with good nutritional properties and higher retained contents of phenolic compounds and antioxidants (present in fruit by-products)
  • Corn based extrudates with fruit-by products included at low levels retained more ß-carotenes.
  • Extrudates containing fruit by-products (particularly with high insoluble fibre content) exhibited decreased porosity.
  • Density of the extrudates increases with increase in byproduct fraction in product formulation.
  • Water Solubility Index of the extrudates decreased with increase in by-product contents in product formulations.
  • Water Absorption Index and hardness of the extrudates increased with increase in by-product amount in product formulations. With fruit pomace incorporated in feed lowers starch content, thereby lowers water absorption rate.
  • Expansion ratio of the extrudates increased at low amount (5 – 10%) of by-products inclusion in product formulations. Small particle sizes (<125µm), dietary (soluble & insoluble) fibres content and chemical composition of fruit by-products also influence the expansion ratio of expanded cereal based snacks¹º.

Influence of dietary fibre from fruit by-products in extruded snack foods

Food industry now focused to reduce consumption of energy dense/ high glycaemic foods through incorporation of dietary fibre rich ingredients in cereal based snacks. Since dietary fibre rich compounds provides low calorie content and health benefits like regulates digestion, improves gastrointestinal and physiological functions, reduces the risk of obesity, cardiovascular diseases, diabetes type 2, body weight management and improves immune system. Fruit by-products contains good amount of dietary (insoluble and soluble) fibre that influences the technological properties of the direct expanded and cereal based snack products. Insoluble fibres of fruit by-products are partially converted into soluble fibres in expanded cereal snacks after extrusion process. Higher amount soluble fibres provide expanded cereal snacks with good nutritional, sensory and techno-functional attributes. Thus dietary fibre of fruit byproducts acts as base material or as starch replacer in RTE/ extruded cereal products with appropriate textural characteristics4. Fibre fortification with fruit by products incorporation can provide alternative way to meet recommended daily intakes (RDI) of dietary fibre and minerals contents through extruded cereal snack foods. According to the Food and Drug Administration (2013), a product with 20% or more fibre content claimed to be “high or good source” of fibre. Recommended daily intake of dietary fibre in a serving size found around 10 – 19% (Selani et al., 2014). Extrudates with 5% fruit by-products claim as good dietary fibre source and extrudes with 10 – 19% fruit by-products claim as high dietary fibre source².

Fruit by-products could be used as an excellent source of nutritionally enhancing and eco-friendly compounds in food industry to provide healthier food products with good consumer acceptability. Utilizing the fruit by-products as ingredients could be a good alternative approach to bring back fruit waste into valued addition and also to increase low cost functional foods in the food market for consumers. Fortification with fruit by-products emerged to be potential healthier option to enhance their nutritional value, increase the dietary fibre content total polyphenol content and antioxidant activity in order to achieve RDI claims in the extruded cereal snack foods.

References available on request