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. 2025 Jun 27;14(7):798.
doi: 10.3390/antiox14070798.

Upcycling of By-Products from Autochthonous Red Grapes and Commercial Apples as Ingredients in Baked Goods: A Comprehensive Study from Processing to Consumer Consumption

Gaetano Cardone  1 , Martina Magni  2 , Veronica Marin  1 , Andrea Pichler  2 , Daniele Zatelli  3 , Peter Robatscher  2 , Ombretta Polenghi  1 , Virna Lucia Cerne  1 , Michael Oberhuber  2 , Silvano Ciani  1
Affiliations

Upcycling of By-Products from Autochthonous Red Grapes and Commercial Apples as Ingredients in Baked Goods: A Comprehensive Study from Processing to Consumer Consumption

Gaetano Cardone et al. Antioxidants (Basel). .

Abstract

Lagrein grape (Vitis vinifera L.) pomace and Scilate apple (Malus domestica Borkh.) skin are polyphenol- and antioxidant-rich by-products with promising applications in the food industry. This study investigated the impact of drying and grinding on their antioxidant properties for use in gluten-free baked goods. Regardless of the by-product analysis, the results showed that processing conditions effectively preserved most of the polyphenols. Furthermore, the grape pomace and apple skin flours produced retained approximately 86% and 66% of anthocyanins, respectively. Incorporating these flours into breadsticks, focaccia, and cookies significantly enhanced their polyphenol content (300-727%), anthocyanin content (600-1718%), and antioxidant capacity (280-1200%). The addition of these by-products to baked goods led to a slight decrease in texture and sensory properties. However, adding both grape pomace and apple skin flours significantly improved consumer acceptance compared to products containing only grape pomace flour. This study highlights the potential of upcycling by-products from grapes and apples to enhance the nutritional profile of gluten-free products while supporting a circular economy approach.

Keywords: UHPLC–MS/MS; apple skin; circular economy; gluten-free; grape pomace; polyphenols.

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Conflict of interest statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: G.C., V.M., S.C., O.P. and V.L.C. were affiliated to the private company that produced the baked goods samples and commissioned the work (Dr. Schär SPA). D.Z. is affiliated to the second private company involved in this study (VOG Products) and provided apple by-products.

Figures

Figure 1
Figure 1
Grape pomace and apple skin flour production. (RT: room temperature).
Figure 2
Figure 2
Hardness (i,iii) and fracturability (ii,iv) of unenriched (black bars) and enriched (white-black bars) breadsticks (i,ii), and cookies (iii,iv) with grape pomace and apple skin flours during storage (t0 = 2 h after baking, t9 and t12 = 9 and 12 months after baking). Different letters (lowercase letters refer to differences between unenriched and enriched sample at the same storage time; capital letters refer to same class of samples during storage) indicate significant differences (one-way ANOVA, Tukey HSD test, p ≤ 0.05).
Figure 3
Figure 3
Sensory evaluation of the breadsticks (a), focaccia (b), and cookies (c) prepared without by-products (unenriched sample; solid line), with grape pomace flour (dotted line), with grape pomace and apple skin flour (dashed line).
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