3.1. Volatile Organic Compounds (VOCs) Analysis
As shown by chromatographic analyses, the volatile compounds determined in the apple pomace extract were mainly esters (6), as well as alcohols (2), and an aldehyde (
Table 2). The highest percentage shares were determined for: hexyl butyrate (37.35%), hexyl hexanoate (12.66%), and butyl hexanoate (11.03%). The analyzed profile of volatile compounds is consistent to some extent with literature data for the ‘Grochówka’ cultivar [
22]. All of the identified compounds were also detected in the raw fruit, but their numbers were significantly reduced. The extract retained those components present at the highest concentrations in the raw fruit, primarily, with lower volatility compounds dominating. The remaining volatile compounds define the extract’s characteristic aromatic profile, which, although still recognizably apple-like, becomes marked by distinctly sweeter, floral, fruity, and tropical nuances of low sensory thresholds. This shift is largely driven by the predominance of hexyl butyrate, whose sweet, fruity, apple-like character imparts a rounded, mellow, and sensorially expressive foundation to the overall aroma. Complementary esters such as butyl butyrate, butyl acetate, and butyl hexanoate further enhance this profile by introducing additional layers of sweetness and tropicality, including subtle banana, pineapple, and berry notes. Simultaneously, the presence of compounds such as hexanal, hexanol, and 2-methylbutanol, associated with green, grassy, woody, and mildly alcoholic tonalities, provides a counterbalancing secondary dimension. Hexanal and hexanol reinforce the fresh, green, apple-skin facets, augmenting the perception of naturalness and freshness, while 2-methylbutanol introduces light ethereal and whiskey-like accents that add complexity without overpowering the dominant fruity signature. Together, these constituents impart a clearly developed and sensorically attractive secondary profile, enhancing the aromatic depth and contributing to the overall structural balance of the extract (
Table 2).
The hydrolate contained esters (3), alcohols (2), and ketones (2) (
Table 3). By far the largest percentage content was that of pinocarvone (52.82%), followed by pinocarveol (15.08%) and pinan-3-one (13.42%). The identified isobutyrates and angelate esters are compounds highly characteristic of the essential oil obtained from Roman chamomile [
23]. Similarly, the main compound, pinocarvone, was identified in essential oil from this plant [
12] as well as pinan-3-one [
24] and pinocarveol [
25].
Table 3.
Content of major volatile compounds and their flavor analyzed in Roman chamomile hydrolate. The data of flavor comes from databases available on the following websites: leffingwell.com, thegoodscentscompany.com. R.T.—retention time; RI exp—experimental retention index; RI lit—retention index from NIST database.
Table 3.
Content of major volatile compounds and their flavor analyzed in Roman chamomile hydrolate. The data of flavor comes from databases available on the following websites: leffingwell.com, thegoodscentscompany.com. R.T.—retention time; RI exp—experimental retention index; RI lit—retention index from NIST database.
| Compound | R.T. [min] | RI Exp | RI Lit | % Content | Flavor | Perception Threshold [ppb] |
|---|
| Isobutyl isobutyrate | 12.32 | 901 | 900 | 1.23 ± 0.02 | fruity, pineapple, tropical | 30 |
| Isopentyl isobutyrate | 13.57 | 996 | 996 | 2.48 ± 0.19 | fruity, ethereal, tropical, green, grape | 40 |
| Isobutyl angelate | 15.63 | 1049 | 1051 | 8.36 ± 0.73 | herbal, green, woody | n/d * |
| Pinocarveol | 17.97 | 1108 | 1111 | 15.08 ± 0.96 | herbal, camphor, woody, pine | 25 |
| Pinocarvone | 18.55 | 1123 | 1124 | 52.82 ± 2.30 | herbal, minty | n/d |
| Pinan-3-one | 19.01 | 1135 | 1134 | 13.42 ± 0.88 | cedar, camphoreous | n/d |
| Borneol | 19.77 | 1154 | 1152 | 2.13 ± 0.17 | camphoreous, herbal, woody | 80 |
| | | % of identified: | 95.52 | | |
Hydrolate is characterized by a distinctly herbal-camphorate aromatic profile, determined primarily by its high pinocarvone content (
Table 3). This gives the composition a cool, slightly minty tone with a distinct sharpness and freshness. A significant pinocarveol content introduces additional herbal, green, and resinous nuances, enhancing the impression of freshness and subtle pine notes. Also, pinan-3-one, on the other hand, accentuates the cool, cedar-camphorate aspects, giving the aroma greater depth, dryness, and woodiness. In the background, delicate, fruity ester notes (including isobutyl isobutyrate and isopentyl isobutyrate) are perceptible, bringing subtle notes of pineapple, grape, and tropical fruit. However, these are merely components of the composition, softening its dominant character and lending it a touch of sweetness and an ethereal lightness. Overall, the scent can be described as intensely herbal, cool, resinous, and camphorous, with distinct woody undertones and a soft, fruity, and tropical aura in the background.
The use of apple extract and chamomile hydrolate, rich in natural fragrance compounds with high sensory acceptability by consumers, allows for a pleasant fragrance profile of the product without the need to introduce additional perfumes into the cosmetic formulation.
An important aspect of cosmetic product safety assessment is the allergen content of raw materials used in the formulation. According to current regulations (Regulation (EC) 1223/2009 [
26] and its amendment, Regulation (EU) 2023/1545 [
27]), all substances classified as fragrance allergens must be listed in the ingredients list if their concentration exceeds 0.001% in leave-on products and 0.01% in rinse-off products. This amendment expanded the list of allergens from 26 to over 80 substances, also including numerous terpenes naturally present in essential oils.
Chamomile essential oil contains several compounds considered allergenic, including linalool, α-pinene, β-pinene, and other monoterpenes typical of plant raw materials. In the case of our chamomile hydrolate, none of the compounds included in the current list of fragrance allergens were detected. Consequently, the hydrolate can be considered a raw material with lower allergenic potential, although reactions to trace amounts of plant ingredients are still possible in individuals with particularly sensitive skin.
3.4. Total Phenolic Content and Antioxidant Potential
The total phenolic content was measured using the Folin–Ciocâlteu assay, which is a technique used to detect the presence of hydroxyl groups in phenolic compounds. In the case of the chamomile hydrolate, analysed in this study, no polyphenols were detected. Furthermore, the polyphenol concentration in the ‘Grochówka’ extract was found to be 2.39 ± 0.30 mg GAE/g extract. Our previous research shows that the value of TPC for the ‘Grochówka’ cultivar was 214.2 mg GAE/100 g of extract, and the average TPC in extracts from the skins of other apple varieties was 173.2 mg GAE/100 g of extract [
6]. These results demonstrate a strong correlation with the values obtained from studies conducted to date. The elevated TPC value is attributable to the high content of gallic and p-coumaric acids, as well as hyperoside and quercetin glycosides, in the skin of the ‘Grochówka’ apple cultivar [
6]. Literature data are very divergent and may differ by up to several orders of magnitude depending on the variety, part of the fruit, analysis method, and the unit in which the results are expressed (equivalent of the standard substance). Research on apple pomace extracts shows values up to even 142.80 ± 26.61 mg GAE/g extract [
28]. A review on apple phenolic compounds has demonstrated that the TPC possibly reaches values as high as 304.66 ± 3.74 mg GAE/100 g or 13.5 gTE/100 g DW [
29].
The ability of the tested extract and hydrolates to scavenge free radicals was determined using the DPPH method. The reducing power was determined using the FRAP method. The DPPH radical scavenging activity of hydrolate from chamomile is at a low level of 5.00 ± 1.25% (3.67 ± 0.04 mM Trolox), whereas the reducing power of the hydrolate determined by the FRAP method is 0.0%. In the case of ethanol extract from ‘Grochówka’, the value of radical scavenging activity was 79.40 ± 2.12% for the 50 mg/mL solution. In comparison, the standard Trolox solution has antioxidant activity at the level of 88.99 ± 5.89%. These results indicate that apple extract has strong antioxidant properties; the assigned value of IC
50 for ‘Grochówka’ extract is 21.5 ± 0.196 mg/mL. Conversely, the reduction power, as measured by the FRAP method, indicates that 50 mg/mL apple extract exhibits 70.56% ± 2.23% reduction. Previous studies have demonstrated the strong antioxidant properties of apple peel extracts, with an average DPPH test value of 892.4 mgTE/100 g of extract [
6]. Studies by Sethi et al. 2020 also confirm the high antioxidant potential of extracts from apple cultivars, with FRAP values of 50.47–192.02 µmol Trolox/g and 71.79–137.66 µmol Trolox/g in peel and cortex [
30]. In contrast, in the DPPH test, the inhibition value was 2.35% for the cortex extract and 274.82% for the peel extract [
30].
The DPPH method is susceptible to even the weakest or slowest-reacting free radical scavengers, which is why a small but measurable amount of antioxidant activity was observed in the chamomile hydrolate sample. At the same time, TPC analysis confirmed the absence of polyphenolic compounds, which are the main group of strong electron donors detected in the FRAP method. Consequently, the FRAP test, which requires effective electron donors, produced a zero result, consistent with the hydrolate’s chemical profile.
A comparison of the results yielded the conclusion that ‘Grochówka’ extract possesses strong antioxidant properties, attributable to the presence of significant amounts of polyphenols and their high chemical activity. The observed consistency between the TPC, DPPH, and FRAP values indicates that phenolic compounds play a dominant role in shaping the antioxidant profile of the analysed extract, and the extract itself can be considered a valuable material with biological potential. The correlation between high FRAP activity and intense DPPH scavenging emphasizes that the extract contains compounds with a multidirectional antioxidant mechanism of action.
Although chamomile hydrolates are often described in the literature as possessing strong antioxidant activity [
10,
12,
14], our results did not confirm this assumption. In the present study, the hydrolate showed negligible radical scavenging ability (DPPH) and no reducing power (FRAP), which is consistent with the absence of detectable polyphenols. This discrepancy may be related to significant differences in the distillation process, plant chemotype, and the limited transfer of non-volatile phenolic compounds into the hydrolate phase [
11,
15]. Moreover, many reports refer to essential oils or alcoholic extracts, rather than hydrolates, which naturally contain much lower concentrations of antioxidant constituents. Therefore, the commonly reported antioxidant potential of chamomile should be interpreted with caution when referring specifically to hydrolates.
3.5. Inhibition of Protease Activity
The precise regulation of the protease-antiprotease balance, encompassing serine proteases and their physiological inhibitors such as α1-antitrypsin and secretory leukocyte protease inhibitor (SLPI), is pivotal to maintaining optimal skin homeostasis [
19]. An imbalance in this system—especially pathological intensification of proteolytic activity—initiates proteolytic degradation of essential components of the extracellular matrix, including collagen and elastin fibers [
31]. The resultant processes include amplification of pro-inflammatory signalling, disruption of tissue architecture, and progressive damage to skin structures. The protease inhibitory activity of chamomile hydrolate is 9.70 ± 1.84%, which is relatively low. In contrast, the inhibitory activity of the extract from ‘Grochówka’ is as high as 60.88 ± 2.35% at a concentration of 1 mg/mL. The determined IC
50 value was at the level of 15.02 ± 0.47 mg/mL (
Table 6). These results indicate that the tested apple pomace extract has relatively high protease-inhibitory properties. When compared with available literature data, the observed effect is of a similar order of magnitude. For example, extracts obtained from different parts of
Crotalaria juncea (flower, leaf, and root) demonstrated inhibitory effects from approximately 68% to 71%, while the positive control (indomethacin) showed the highest inhibition (almost 95%) [
19]. Although direct comparison should be made cautiously due to differences in plant matrix, extraction procedures, and assay conditions, the activity recorded for the ‘Grochówka’ pomace extract falls within a comparable range, supporting its potential as a source of protease-inhibitory constituents.
3.6. Inhibition of Lipase Activity
For healthy, non-irritated skin and its microbiome, the physiological composition of saturated and unsaturated free fatty acids plays an important role. Regulating lipolytic activity in the skin may play a significant role in maintaining the appropriate composition of free fatty acids produced and secreted by the skin. This process might reduce inflammation, which is particularly important in the care of oily and acne-prone skin as well as skin affected by atopic dermatitis. Therefore, the ability of some compounds and mixtures to inhibit lipase activity may be considered a potentially beneficial cosmetic property. However, this effect should not be too strong or non-selective, as excessive inhibition of lipolysis can lead to lipid imbalance and a weakened skin barrier [
32].
The lipase inhibitory test showed that roman chamomile hydrolate was 26.31 ± 2.44%. In the case of the inhibitory properties of the ‘Grochówka’ extract at a concentration of 1 mg/mL, only a 10.02 ± 1.20% inhibition of lipase activity was achieved. In this case, the IC
50 parameter value is 52.4 ± 0.544 mg/mL (
Table 6). When compared with literature data, the observed inhibitory activity may be considered moderate. For example, solvent fractions obtained from
Polygonum cuspidatum demonstrated markedly stronger effects at a lower concentration (0.1 mg/mL), with inhibitory activity ranging from approximately 78% to 86%, depending on the fraction, while the positive control (orlistat) reached 98.18 ± 0.18% inhibition [
20].
In contrast to highly concentrated solvent fractions designed to maximize enzyme inhibition, the apple pomace extract and chamomile hydrolate evaluated in the present study represent less purified, cosmetically relevant raw materials. From a dermatological perspective, their moderate lipase-inhibitory activity may be advantageous, as it suggests a regulatory rather than strongly suppressive effect on lipolysis. Such a profile may support sebum balance without excessively disrupting physiological lipid metabolism.
In the present study, the enzyme inhibition assays were performed at 1 mg/mL, a concentration commonly used in preliminary screening of plant extracts, intended to evaluate their intrinsic bioactivity rather than to directly reflect concentrations used in final cosmetic formulations.
The inhibitory effects observed for protease and lipase may be associated with the presence of phenolic compounds and triterpenoid constituents known to occur in apple-derived materials. Apple pomace is particularly rich in polyphenols such as chlorogenic acid, catechin, epicatechin, procyanidins, and quercetin (both free and bound in the form of glycosides), which have been reported in the literature to interact with enzymatic proteins [
33,
34]. These compounds may form hydrogen bonds or hydrophobic interactions with amino acid residues located in or near the catalytic site of enzymes, which can partially block substrate access or induce conformational changes in the enzyme structure, leading to reduced catalytic activity [
35,
36].
In addition, apple pomace extract contains pentacyclic triterpenoids such as ursolic and oleanolic acids. These compounds have also been reported as inhibitors of several hydrolytic enzymes, including lipases and proteases [
37,
38]. Their relatively hydrophobic structure enables interactions with enzyme active sites and may interfere with substrate binding [
39]. Therefore, the inhibitory activity observed in the present study is likely the result of the combined action of multiple classes of bioactive compounds naturally present in the apple pomace extract.
3.7. Physicochemical Parameters of Cosmetics
As part of the research, a cosmetic emulsion formula was designed based on roman chamomile hydrolate and extract from ‘Grochówka’ pomace. The control emulsion (E1), which did not contain these ingredients, exhibited a visibly lighter color (parameter L*) compared with the formulation enriched with chamomile hydrolate and apple extract (E2,
Figure 1,
Table 7). This difference is expected, as the extract itself has a strong natural pigmentation. The instrumental parameters revealed a measurable difference between the formulations, with a ΔE of 8.24, indicating a significant dissimilarity between the two colours. The b* parameter, corresponding to the yellow-blue axis, further confirmed the impact of the extract on color, as E2 demonstrated a markedly higher b* value (11.67) compared with the base emulsion (5.20). This shift toward the yellow region may result from the presence of rutin and quercetin, compounds abundant in apple peels—particularly in traditional cultivars such as ‘Grochówka’ [
6]—and known for their characteristic yellowish chromatic contribution due to their flavonol structure. Importantly, the yellowish tone of E2 (
Figure 1) did not translate to visible staining or colour transfer on the skin.
Both formulations successfully passed stability tests, exhibiting no observable deviations in color, consistency, odor, or phase separation throughout the evaluation period. No signs of instability or other concerning changes were detected, indicating that the samples maintained their physicochemical integrity.
Physiochemical parameters such as density (0.959 g/mL for E1 and 0.967 g/mL for E2) as well as viscosity (39,180 cP for E1 and 37,980 cP for E2) are characteristic of care products in the form of emulsions. Slight differences in the obtained results may indicate that the addition of extract from ‘Grochówka’ pomace and roman chamomile hydrolate does not disturb the structure of the cosmetic/emulsion and does not affect its rheology.
Both emulsions exhibited a pH close to 5.5, which is within the physiological range of the stratum corneum, indicating that the addition of hydrolate and apple extract did not compromise the formulation’s dermatological safety and did not need to adjust the pH regulator’s concentration further. Most experts agree that the optimal pH of the topically used skin formulation should be within the range of 4–6 to assure homeostasis and barrier permeability of the skin [
40]. Several recent formulation papers report that oil-in-water creams enriched with botanical extracts exhibit a similar mildly acidic pH [
41,
42].
The results for viscosity show no statistical differences between the two emulsions, indicating no meaningful effect of the added hydrolate and apple extract on the rheological behavior of the formulation. Although a literature search revealed no studies reporting the viscosity of creams enriched with apple extracts or chamomile hydrolates, the viscosity we observed falls within the range typical for herbal emulsions. For example, a polyherbal cream containing aloe vera gel and turmeric extract exhibited a viscosity of about 41,000 cP at 20 rpm—a value comparable to those seen in this formulation [
43].
3.8. Assessment of Cosmetic Impact on Condition and Quality of Skin
Due to the split-face design, each participant served as their own control, which increases statistical sensitivity and allows detection of treatment-related changes. Improvement of skin moisture for cosmetics based on Roman chamomile hydrolate and enriched with apple pomace extract was observed up to 24.6% and 25.2% after 7 and 14 days of application, respectively, whereas control emulsions achieved a degree of hydration at the level of around 17% (
Figure 2). Apple pomace extract is rich in pectins and polysaccharides, which might increase water-binding capacity and act as humectants. The results are in line with [
44], where dermocosmetic creams enriched with wild apple extracts increased hydration in in vivo tests. Due to the high phenolic content and strong radical-scavenging activity of apple extract, ROS-driven lipid peroxidation in the stratum corneum can be limited, helping to preserve barrier lipids and moisturising factors. These results are comparable to those reported in an in vivo trial of creams containing wild apple extract, where a 28-day application increased hydration by 21.19 ± 7.59% to 29.60 ± 10.95% depending on extract concentration [
44]. In this study, the authors observed no significant changes in transepidermal water loss or skin pH during use. Another work shows that application of a cream enriched with wild apple fruit extract assured improved skin hydration by 18.52 ± 11.51% after 14 days and 16.52 ± 9.36% after 28 days of application [
45]. The similarity suggests that pectins and polysaccharides of apple pomace act as humectants and improve skin hydration; however, the final effect depends also on other constituents of the emulsion.
Inflammation in skin was markedly reduced in both emulsions, with E2 being more effective (−13.2% vs. −8.1% for control emulsion in day 7 and −15.3% vs. −9.3% for control emulsion in day 14). Chamomile is known for its ability to inhibit COX-2 [
46] and suppress pro-inflammatory cytokines [
47], which might have led to reduced skin microirritation. In this study, it was also proven that chamomile hydrolate presents LOX inhibition, and so, it limits peroxidation of sebum and formation of pro-inflammatory lipid mediators around follicles, which is essential in comedogenesis and acne [
48]. It was demonstrated before that extracts derived from
Malus domestica cv. ‘Grochówka’ has proapoptotic and cytoprotective properties in human-originated Caco-2 and HepG2 cell lines, further supporting the gathered results [
6].
Similarly, skin sensitivity decreased with both formulations, although the reduction was more pronounced with E2. On day 7, sensitivity dropped by 7.4% for E2 compared to 4.4% for E1, and on day 14 by 5.3% vs. 3.2%, respectively. Chamomile is widely recognized for its soothing properties, particularly due to the presence of α-bisabolol and chamazulene—compounds that inhibit the production of prostaglandins and leukotrienes [
49]. The results demonstrate that even in hydrolate form, chamomile retains measurable anti-irritant activity.
Both emulsions improved skin elasticity, with increases ranging from 14 to 19% across the study period. The enriched formulation showed better performance on day 7 (+17.3% vs. +14.2% for E1), with no statistically significant differences between the emulsions after another 7 days.
The melanin index decreased with E1 (−2.1 at day 7 and −1.7 at day 14) but showed slight increases with E2 (+1.3 and +0.8). There are studies showing that ethanol extracts from apple flesh and peel exhibit a whitening effect in vitro by decreasing melanin synthesis in B16/F10 melanoma cells [
50]; however, this effect is strictly concentration-dependent. The lightening effect of apple extracts could require several weeks of continuous use. In the two-week trial, the sustainable formulation did not reduce melanin, and the slight increase observed may reflect short treatment duration. Longer studies are necessary to determine whether apple extract-enriched emulsion may cause visible depigmentation.
When it comes to pore size, emulsion E1 caused minimal or inconsistent changes (+1.7% on day 7; −2.3% on day 14) while E2 significantly reduced pore visibility by 12.1% and 8.9% at the same timepoints. Apples are rich in tannins [
51,
52,
53]—compounds containing multiple hydroxyl groups that form protein complexes in the skin, resulting in astringent activity. Gathered results suggest that apple extracts could be used in cosmetics to reduce pore size and sebum secretion.
Our research addresses the current needs of the cosmetics industry in the search for innovative, sustainable, and functional raw materials of natural origin. It demonstrates the high utility of agri-food industry by-products as valuable ingredients with significant biological potential, supporting the principles of a circular economy. The article also highlights the potential for reducing waste and the consumption of primary resources in cosmetics production processes. The presented results constitute a valuable scientific and practical contribution, responding to the growing expectations of environmentally conscious consumers and producers. However, these findings should be interpreted with caution due to the exploratory nature of the study, the relatively small sample size (n = 10), and the short duration of treatment. Larger and longer-term clinical studies are required to confirm the observed effects.