# Functionality of Muffins Fortified with Apple Pomace: Nutritional, Textural, and Sensory Aspects
## 3 Results and Discussion
### Volatile Compounds Determined from Apple Pomace before and after Its Processing into Powder
Following the heat treatment, changes occurred regarding the concentration of compounds in the alcohol class as follows: the 1-hexanol content increased, reaching the value of 20.98%; new compounds of this class appeared, namely 2-Methyl-1-butanol, which gives an odor of pleasant and 1-Octen-3-ol, which imprints an aroma of mushroom, green, and vegetative. Aldehydes and ketones derive mainly from the catabolism of fatty acids but can derive from branched-chain amino acids such as isoleucine, valine, and leucine. There are reports of more than 25 aldehydes in apple fruits, but in our study the following aldehydes were determined in the by-products and the powders of apple pomace: hexanal, 51.37% in the by-product and 24.43% in the powder, developing aroma such as fresh, green/sharp, earthy overall intensity good, green apple, fruity, and grass-like [28]; 2-Hexenal was 1.44% in the by-product and undetectable in the powder, this being associated with a smell of green apple. 5-Hepten-2-one accounted for 4.97% in the by-product and a lower amount in the powder, while low amounts of nonanal 0.19% were detected in the by-product, the odor perception being that of aldehyde, rose, waxy, citrus, orange, and floral, a higher amount being detected for the powder. Heptanal was determined in lower amounts in the by-products in comparison to the powder, giving an aroma of soap, orange peel, and allow. Benzaldehyde was determined in low amounts in the by-product, 0.53%, but increased a lot in the thermally treated sample, the powder presenting a very high benzaldehyde content of 30.46%. Benzaldehyde is the volatile compound responsible for a typical cherry aroma and can be synthesized from amino acids (aromatic amino acid and phenylalanine) [29]. The rest of the identified compounds were lower in content, such asacotophenone (0.12% in the by-product and ND in the powder) could lead to a perception of floral and almond odors. Terpenes and terpenoids are compounds identified both in the by-product obtained from the processing of apple fruits and the powder. beta-Myrccene 0.14% is associated with balsamic, must, and spice odors; limonene was also detected at 0.57% level in the by-product, conferring an aroma of citrus and mint; another therpene, alpha-Pinene, was also detected but only in the by-product at a level of 0.21%, offering pine, turpentine green- floral, herbaceous, sweet, warm, and woody aromas. The most abundant acid found in the by-product of apple processing is butanoic acid, hexyl ester, or hexyl butyrate at 4.44%, which belongs to the class of organic compounds \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Volatile Compounds** & **Odor Perception** & **Raw By-Product** & **Apple Pomace Powder** \\ \hline Miscellaneous compound & & & \\ \hline Toluene & Nf & N.D. & 0.13 \\ Furfural & Sweet Woody, Almond, Fragrant, Baked Bread & N.D. & 5.19 \\
2-Pentyfuran & Sweet & N.D. & 1.6 \\ Styrene & Sweet, Balsamic, Floral, Plastic & 0.44 & N.D. \\ Isopentyl hexanoate & Sweet, Fruity & 0.08 & N.D. \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._known as fatty acid esters. Hexyl butyrate has a sweet, slightly waxy, fruity, apple, and apple peel aroma, with a similar green/soapy taste. Another important acid is hexanoic acid at 2.61%, having as its perception sour, fat, sweat, and cheesy odors. The rest of the acids are in lower concentrations, according to Table 5.  
Following the drying operation at 80 \({}^{\circ}\)C, new compounds appeared, such as the following: D-Limonene at 5.36%, associated with a lemon and orange aroma; beta-Pinene was also at a low content of 0.2%, leading to a fresh minty, eucalyptus, and camphoraceous note with a spicy, peppery, and nutmeg nuance; alpha-Terpineol was found at 0.31% with an oily, anise, minty, and peach-like odor, but also other compounds were present, such as beta-Linalool at 0.29% and p-Cymene at 0.11%. In the powder obtained from the thermally treated sample, the compound furfural was also detected at a level of 5.19 %.