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Apple peel as a source of fibre in sweet bakery

In the food industry, the production of bakery and confectionery products accounts for 37% of food and beverage companies, in which high amounts of refined sugar are used.
Today, there are alternative solutions to introduce functional ingredients in sweet preparations, which improve nutritional quality and facilitate the development of healthy novel foods. One of these options is powdered apple peel, which is rich in fibres, minerals and polyphenols, and can be used as an ingredient in the preparation of cookies or muffins, as reflected in several studies in recent years.

Apple peel as a functional ingredient

The apple (Malus domestica) is the fruit of the common apple tree whose cultivation dates back 15,000 years. This fruit has usually been used for different types of elaborations: from its fresh consumption to the production of cider or preserves, to famous desserts such as the traditional Apfelstrüdel or our grandmother’s apple pie.
During the processing and transformation of the apple, the peel, which is naturally rich in fibre, minerals and polyphenols, is usually discarded as a by-product with no apparent use. However, this preconceived idea is changing.

“Apple skin, usually discarded as a by-product, can be used as a functional ingredient in confectionery production.”

Agrosingularity works with powdered apple peel discarded as a by-product, which has a characteristic green colour depending on the variety, with a slightly acid flavour and aroma. It also has:

High fiber content, 63.8%
High protein content, 10%
High antioxidant capacity

Thanks to its texturizing and antioxidant properties, it can be used in the food industry in baking, beverages, snacks and healthy products. It is suitable for the entire population and any type of diet.
It should be mentioned that Agrosingularity apple peel has twice the fiber of that observed in previous scientific studies [1], which positions the product as Premium and of high quality.

Why should we use apple skin in bakery and confectionery?

There are several studies in recent years [1,2] that have positioned the powdered apple peel as a functional ingredient with remarkable properties and benefits both from an industrial and processing point of view, as well as nutritional and health properties for the end customer.

For example, a study carried out on the preparation of muffins [2] found that the addition of powdered apple peel in 16%, showed satisfactory results from the sensory point of view when evaluated by an expert tasting panel.

In another study carried out adding apple peel to cookies [1] the results are even more conclusive. First of all, in the basic analysis of white wheat flour versus apple peel of the red skin variety, surprising results are obtained, since powdered apple peel has:

4 times less humidity
10 times more lipids
8 times more soluble fiber
5 times more insoluble fibre
10 times more than total phenols
20 times higher antioxidant capacity measured by the FRAP test

In this test, cookies were made with increasing amounts of powdered apple peel in their composition. Subsequently, the nutritional and sensory quality of the result was studied compared to the control only with white wheat flour.

1. Processing characteristics

By increasing the amount of powdered apple peel in the dough, a decrease in viscosity and the breaking point or “breakdown” is observed, while the gelation temperature increases. This is due to the high percentage of fibre in the apple skin, especially pectin, which absorbs water and reduces the amount of water available for the starch granules, thus limiting the growth of the dough.

2. Physical characteristics

The thickness and volume of the biscuits progressively decreases as powdered apple peel is added to the samples. This is due to the amount of fibre (44%) naturally present, which in the dough dilutes the protein content and interferes with the formation of the gluten matrix.

As for the color of the cookies, these become darker with increasing amounts of powdered apple peel, due to the greater presence of polyphenols that favor the enzymatic reactions of darkening of the dough.

3. Chemical characteristics

Moisture progressively increases in the dough as the amount of powdered apple peel added increases, thanks to the fibre’s water retention capacity. The same happens with the lipid content, whose gradual increase grows with the addition of increasing amounts, facilitating the plasticity of the dough, air retention, taste and appearance, thanks to the richness of unsaturated phospholipids and galactolipids.

“Fibre lowers the energy value of cookies made”

As for fibre, this also reflects an increase in line with the addition of powdered apple peel, especially the soluble fraction, which may represent 73% of the total fibre. Biscuit samples made with 4 or 8% apple peel can be named as “source of fibre” and those with 16, 24 or 32% as “high fibre content” according to Regulation (EC) 1924/2006 .

4. Antioxidant characteristic

Even with small amounts of powdered apple peel the total polyphenol content increases considerably, making it an efficient tool to improve the nutritional and healthy quality of sweet products such as cookies.

The same happens with the antioxidant capacity of the dough, measured through the DPPH and FRAP tests, which improves with the addition of increasing amounts.

5. Sensory characteristics

The sensory evaluation of elaborations with new ingredients is fundamental to know the acceptance by the final consumer. Consumers usually view the incorporation of new ingredients of plant origin in confectionery as positive as long as the taste and texture are not clearly affected.

“The icing on the cake in the development of a novel food is an excellent sensory analysis”

Adding powdered apple peel to cookies improves aroma and flavor without affecting internal structure or appearance. The best results were obtained by adding 24% of powder, with an exceptional appearance, internal structure, texture and flavour, being viable the development of a new food product.

Conclusions

  • Powdered apple peel is rich in fibre, polyphenols and minerals, and when added to the preparation of bakery products such as cookies or muffins, it improves moisture, texture, fiber content, total polyphenols and antioxidant capacity.
  • A 24% apple peel powder allows to obtain the best results in terms of both the dough-making and nutritional and sensory characteristics in biscuits.
  • Powdered apple peel is an outstanding functional ingredient for novel food innovation and development.

References:

[1] Najov et al., 2020. Influence of Apple peel powder addition on the physico-chemical characteristics and nutritional quality of bread wheat cookies. Food Science and Technology International 26(7): 574-582

[2] Rupasinghe et al., 2009. Baking and sensory characteristics of muffins incorporated with Apple skin powder. Journal of Food Quality 32: 685-694.