Production of Lactic Acid Wort-Based Beverages with Rosehip, Lemongrass, and Eucalyptus Oils

Abstract

Rosehip, lemongrass, and eucalyptus oil was studied for the first time as a strategy for improvement of lactic acid wort-based beverage characteristics. Each oil was added to wort at doses of 0.01%, 0.02%, and 0.03% (v/v) by vigorous shaking to ensure homogenous distribution, and fermentation was carried out with Lacticaseibacillus casei spp. rhamnosus Oly at 25 ± 1 °C for 48 h. Oil addition influenced microbial growth, phenolic composition, antioxidant activity, and sensory quality. Although higher oil concentrations reduced lactic acid bacteria viability, in all the beverages the concentration of viable lactic acid bacteria cells was above 10⁷ CFU/mL. Total phenolic content and phenolic acids increased after fermentation, although flavonoid levels were largely unaffected. Antioxidant activity showed assay-dependent trends, with decreases observed in ABTS measurements during lactic acid fermentation, whereas CUPRAC values remained stable or slightly improved. Sensory evaluation revealed that all the beverages with eucalyptus oil received lower scores than the control sample. Rosehip oil enhanced flavor only at a concentration of 0.03%, while lemongrass oil at 0.02% provided the best balance of aroma, taste, and overall impression. Based on combined chemical, microbiological, and sensory outcomes, 0.02% lemongrass oil was identified as the most promising candidate for further development.

1. Introduction

The growing demand for non-dairy fermented beverages has increased interest in cereal-based substrates, including wort, which provide suitable nutrients for lactic acid bacteria (LAB) and allow the production of stable, mildly acidic, non-alcoholic drinks. The health benefits of consuming lactic acid fermented beverages include increased antioxidant activity resulting from the production of biologically active substances, such as phenolics and flavonoids. In addition, LAB-fermented beverages may contribute to the management of metabolic and cardiovascular disorders. To exert probiotic or nutraceutical effects, LAB levels should reach at least 10⁶ CFU/mL or g. Despite their technological advantages, LAB-fermented wort beverages often exhibit limited aroma complexity and an overly sour profile, reducing consumer acceptance [1,2,3,4].

To overcome sensory limitations and at the same time increase antioxidant potential, researchers have investigated the addition of botanical ingredients such as cold-pressed oils and essential oils to fermented matrices. The sensory profile of cold-pressed oils reflects the distinctive flavors and aromas of the seeds or fruits from which they are derived. Moreover, they are source of different biologically active substances such as vitamins, minerals, phytosterols, tocopherols, carotenoids, and polyphenols [5]. Essential oils are complex mixtures of volatiles (terpenes, aldehydes, phenolics) that can act both as flavoring agents and as sources of bioactive compounds with antioxidant and antimicrobial activities; however, because essential oils may also inhibit LAB at higher concentrations, their selection and dosage must be tailored to preserve fermentation performance [6].

Although the combination between lactic acid fermentation of wort with low-level addition of essential or cold-pressed oils offers a route to develop sensorially attractive and functionally enriched non-alcoholic beverages, there is scarce data on such beverages in the scientific literature. Goranov et al. [7] and Trendafilova et al. [4] investigated production of lactic acid wort-based beverage with mint essential oil with and without stirring. Goranov et al. [8] also investigated the effect of raspberry seed oil on lactic acid fermentation of wort. However, there is no data about the production of lactic acid wort-based beverages with the addition of rosehip, lemongrass, and eucalyptus oils.

Rosehip (Rosa canina L.) cold-pressed oil is distinguished by its rich content of polyunsaturated fatty acids, linoleic acid, linolenic acid, and phytosterols, mainly β-sitosterol. The rosehip seed contains valuable phytochemicals such as phenolic compounds, carotenoids, and ascorbic acid. This provides an opportunity to enhance the nutritional profile of beverages but also to improve their oxidative stability and shelf life [9,10,11].

Lemongrass (Cymbopogon citratus) essential oil is rich in citral (geranial and neral), which imparts its characteristic lemony aroma and flavor, making it particularly appealing for flavoring and scenting purposes in the food and beverage industry. Beyond its sensory attributes, lemongrass oil exhibits significant antioxidant, antimicrobial, and anti-inflammatory properties, attributed to its diverse phytochemical composition. With the use of lemongrass essential oil as preservative, the acceptable daily intake of citral is 0.5 mg/kg bw/day [12,13,14].

Eucalyptus (Eucalyptus globulus) essential oil is known for its high content of eucalyptol (1,8-cineole), which accounts for its antimicrobial, anti-inflammatory, and analgesic properties. The chemical composition can vary depending on the eucalyptus species, but significant components may include α-pinene, limonene, and globulol. However, due to the potential toxicity of eucalyptol if improperly used, the application of eucalyptus essential oil in functional foods requires careful formulation and adherence to safety guidelines [15,16,17].

The differing volatile compositions make these three oils suitable candidates for evaluating how botanical additions affect microbial performance and beverage sensory properties. Therefore, this study aims to evaluate the effect of rosehip, lemongrass, and eucalyptus oil addition on some basic fermentation parameters (pH drop, residual extract, and LAB viability), phenolic compounds content, antioxidant capacity, and sensory acceptance of beverages produced. We hypothesize that carefully dosed additions of these botanicals will improve overall beverage acceptability and its biological value.

2. Materials and Methods

2.1. Raw Materials, Media, and Reagents

2.1.1. Raw Materials

The strain used in this study was Lacticaseibacillus casei spp. rhamnosus Oly, isolated from spontaneously fermented yoghurt from Romania, and its characteristics were described in Ahmedova et al. [18]. Pilsen, Vienna, and Caramel Munich II malts were purchased from Bestmalt, Germany. The oils from rosehip (Zdravnitsa, Sofia, Bulgaria), lemongrass (Kateko, Plovdiv, Bulgaria), and eucalyptus (Bulgarian rose Plc, Karlovo, Bulgaria) were purchased at a local market.

2.1.2. Media

MRS broth and LAPTg10 Agar were used for cultivation and enumeration of LAB cells, respectively. They had the following composition (g/L):

MRS Broth: peptone from casein—10; yeast extract—4; meat extract—8; glucose—20; K₂HPO₄—2; sodium acetate—5; diammonium citrate—2; MgSO₄—0.2; MnSO₄—0.04; Tween 80—1 mL/L; pH = 6.5. Sterilization—15 min at 118 °C.

LAPTg10 Agar: peptone—15; yeast extract—10; tryptone—10; glucose—10; Tween 80—1 mL/L; agar—15; pH = 6.6–6.8. Sterilization—20 min at 121 °C.

2.1.3. Reagents

Gallic acid, quercetin, caffeic acid, neocuproine, ABTS (2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), and Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid) were purchased from Sigma Aldrich, St. Louise, MO, USA. Hydrochloric acid was bought from Merck, Darmstadt, Germany. All the other reagents were of analytical grade.

2.2. Wort Production

A hand disc mill (Corona, Germany) was used for milling a 4.5 kg mixture of 60% Pilsen, 20% Vienna, and 20% Caramel Munich II malts. The milled malt was then mixed with water in a ratio of 1:5. Mashing was carried out in a 20 L laboratory scale brewery Braumeister (Speidel, Ofterdingen, Germany) by heating at a rate of 1.5 °C/min, with rests of 30 min at 50 °C and 60 min at 77 °C. After wort separation, boiling was conducted without hop addition for approximately 30 min in the same system. Hot trub was removed and the wort was autoclaved at 121 °C for 30 min for storage prior to experimentation. It was then aseptically filtered and used for lactic acid fermentation. The wort parameters were extract—13.0 ± 0.2 °P and pH—5.00 ± 0.05.

2.3. Fermentation

Oils from rosehip, lemongrass, and eucalyptus were added in a concentration of 0.01%, 0.02%, and 0.03% (v/v), mixed by vigorous shaking to ensure homogenous distribution to 200 mL of wort, and poured in plastic bottles. Wort was inoculated with 2% (v/v) lactic acid bacteria suspension. The amount of lactic acid bacteria suspension was determined on the basis of preliminary trials. Lactic acid bacteria were pre-inoculated in MRS broth and incubated at 37 ± 1 °C for 24 h to obtain initial concentration of 10⁷ cells/mL. Fermentation was conducted at 25 ± 1 °C and it lasted 48 h. Fermentation duration was determined on the basis of pH drop. Wort without oil addition was fermented under the same conditions and was used as a control sample.

2.4. Analytical Procedures

2.4.1. Fermentation Parameters

The extracts of wort and lactic acid wort-based beverages were measured by means of a densitometer Anton Paar DMA 35 (Anton Paar, Graz, Austria), and the pH was measured with Bante PHS-3BW benchtop pH meter (Bante, Shanghai, China). The enumeration of viable lactic acid bacteria was made by preparing appropriate 10-fold dilutions, which were plated on LAPTg10 agar, and incubated for 48–72 h at 37 ± 1 °C until the appearance of countable single lactic acid bacteria colonies. Fermentation parameters were monitored daily.

2.4.2. Phenolic Content and Antioxidant Capacity of the Beverages Produced

The wort and lactic acid beverages were diluted with methanol in ratios of 1:4 and 1:9 for analyzing phenolic compounds and antioxidant activity, respectively. After waiting for 30 min, they were filtered with Whattman No. 1 filter paper. Total phenolic compounds, phenolic acids, and flavonoids were determined by the modified Glories method on a Shimadzu UV-VIS1800 spectrophotometer (Shimadzu, Kyoto, Japan) according to Shopska et al. [19]. The antioxidant activity was assessed using cupric reducing antioxidant capacity (CUPRAC) and ABTS radical scavenging activity on the abovementioned spectrophotometer according to Shopska et al. [19]. For the ABTS method, ABTS stock solution was prepared by combining equal volumes of 7 mM ABTS solution and 2.45 mM potassium persulfate solution and keeping the mixture in the dark for 12–16 h. The mixture was subsequently prepared as a 1:30 dilution in methanol to achieve an absorbance of 1.1 ± 0.1 at 734 nm. For the assay, 0.15 mL of the methanolic sample extract (or methanol for the blank) was mixed with 2.85 mL of the diluted ABTS reagent. The reaction mixture was kept in the dark for 30 min, after which its absorbance at 734 nm was measured. The antioxidant activity was measured using a calibration curve and given as µM TROLOX equivalent/L [19]. For CUPRAC methods, the reaction mixtures were obtained by combining 1 mL of 0.01 M CuCl₂·2H₂O, 1 mL of ammonium acetate buffer (pH 7), 1 mL of a 7.5 mM neocuproine solution in ethanol, 0.5 mL of the methanolic extract, and 0.6 mL distilled water. After a 30 min incubation period, the absorbance at 450 nm was measured using a blank prepared with distilled water. The antioxidant activity was determined from the calibration curve and expressed as μM TROLOX equivalent/L [19].

2.4.3. Sensory Analysis

A sensory evaluation of the beverages was carried out by a trained, 6-member tasting panel, consisting of 4 males and 2 females. The panel consisted of members of different age groups (aged 21–60). Prior to the formal sensory analysis, panelists underwent training in basic aroma recognition and scale usage. The training consisted of three one-hour sessions, during which representative samples illustrating wort aroma and taste, lactic acid aroma and flavor, and the aromas of rosehip, lemongrass, and eucalyptus oils were provided. Tastings were conducted in a sensory evaluation room, with samples poured into clean, transparent glasses. Each sample was assigned a number and evaluated in triplicate. Panelists were provided with flat mineral water and plain white bread to cleanse the palate between samples. All tastings were performed using cold beverages (4 °C). Samples were assessed for taste and aroma using descriptive analysis (method 13.10) and the ranking method (method 13.11) [20]. Each sample was evaluated in three replicated sessions in randomized order. Each sensory attribute was scored on a ten-point intensity scale, where 1 indicated ‘extremely low’ and 10 indicated ‘extremely strong’.

2.4.4. Statistical Analysis

All results are presented as mean ± standard deviation of three replicates, calculated by Microsoft Excel 2016. To assess the effect of sample type on the measured parameters, data were analyzed by one-way analysis of variance (ANOVA). When significant differences were detected, Tukey’s HSD post hoc test was applied at a significance level of p < 0.05. Statistical analyses were performed using Microsoft Excel.

3. Results

3.1. Effect of Oil Additions on the Fermentation Parameters

The effect of the addition of rosehip, lemongrass, and eucalyptus oils on the fermentation was investigated by measuring the extract, the pH, and the viable lactic acid bacteria concentration at the beginning (0th h) and at the end (48th h) of fermentation. The results were compared to a control without any oil addition and are presented in

Table 1. Effect of the addition of rosehip, lemongrass, and eucalyptus oil on the changes in the main beverage parameters during fermentation.

Oil Concentration	Sample	Extract		pH		Number of Viable LAB Cells
% (v/v)		°P		-		logN
		0 h	48 h	0 h	48 h	0 h	48 h
-	Control	12.77 ± 0.38 a	12.62 ± 0.29 a	4.99 ± 0.05 b	3.77 ± 0.05 c	7.54 ± 0.22 e	9.04 ± 0.33 h
0.01	Rosehip oil	13.00 ± 0.39 a	12.77 ± 0.33 a	4.96 ± 0.03 b	3.72 ± 0.0 c	7.18 ± 0.32 f	8.49 ± 0.43 hi
0.02		12.84 ± 0.25 a	12.67 ± 0.32 a	4.95 ± 0.04 b	3.72 ± 0.06 c	7.26 ± 0.21 g	7.04 ± 0.36 j
0.03		12.91 ± 0.33 a	12.72 ± 0.32 a	4.95 ± 0.03 b	3.73 ± 0.03 c	7.35 ± 0.26 fg	7.18 ± 0.38 j
0.01	Lemongrass oil	12.74 ± 0.33 a	12.60 ± 0.33 a	4.84 ± 0.06 b	3.85 ± 0.04 c	7.45 ± 0.29 f	8.40 ± 0.43 hi
0.02		12.77 ± 0.38 a	12.62 ± 0.31 a	4.97 ± 0.05 b	3.84 ± 0.05 c	7.27 ± 0.32 f	8.48 ± 0.39 hi
0.03		12.86 ± 0.34 a	12.81 ± 0.34 a	4.95 ± 0.02 b	4.45 ± 0.04 d	7.43 ± 0.22 f	7.00 ± 0.42 j
0.01	Eucalyptus oil	12.96 ± 0.26 a	12.77 ± 0.35 a	4.95 ± 0.06 b	3.73 ± 0.07 c	7.79 ± 0.26 ef	8.18 ± 0.38 i
0.02		12.74 ± 0.36 a	12.60 ± 0.36 a	4.95 ± 0.06 b	3.84 ± 0.06 c	7.57 ± 0.27 f	8.00 ± 0.46 i
0.03		12.72 ± 0.29 a	12.60 ± 0.35 a	4.90 ± 0.09 b	3.83 ± 0.05 c	7.49 ± 0.26 f	8.00 ± 0.39 i

Each value is the mean ± SD of triplicate determination. Different letters for the values of the samples in the column indicate significant statistical differences (p < 0.05).

. Overall, the extract consumption by LAB ranged between 0.1 °P and 0.2 °P, which is consistent with the limited availability of fermentable sugars in the wort used. Moreover, the statistical analysis showed that there was no significant difference between the extract between and after lactic acid fermentation. Glucose, fructose, and sucrose are the primary carbohydrates metabolized by LAB [21], but according to Ivanov et al. [22], the wort prepared by this mashing method contains only about 7% glucose and less than 1% fructose, explaining the low overall extract reduction observed.

The addition of 0.03% lemongrass oil significantly inhibited fermentation, as indicated by the lowest pH drop (from 4.95 to 4.45) and limited extract consumption. In the other variants, the pH drop ranged from 1.0 to 1.2 units, suggesting active lactic acid production.

The number of viable LAB cells increased by approximately 1.5 log units in the control sample, while the oil-supplemented variants exhibited lower growth rates. Even at the lowest concentration (0.01%), both essential and cold-pressed oils reduced LAB proliferation, resulting in increases of only 0.4–1.3 log units, depending on the oil type. Increasing the concentration of rosehip oil further decreased cell viability, whereas higher levels of eucalyptus oil did not significantly affect microbial growth. Interestingly, 0.02% lemongrass oil stimulated LAB activity to a greater extent than the 0.01% addition, while 0.03% lemongrass oil led to the lowest final LAB counts. The observed inhibitory effect for the highest concentration of lemongrass oil is likely associated with its high citral content, which is known to disrupt cell membrane integrity and proton gradients [23]. Despite these effects, all beverages can still be considered functional, as final LAB counts exceeded 10⁷ CFU/mL, the generally accepted minimum threshold for probiotic efficacy in fermented beverages.

3.2. Effect of Oil Addition on the Phenolic Compounds Content

Phenolic compounds have received considerable attention due to their antioxidant and free radical scavenging activities, which potentially have beneficial implications in human health [24]. The results for the total phenolic compounds (TPC), phenolic acids, and flavonoids are presented in Figure 1, Figure 2 and Figure 3, respectively. Overall, the TPC concentration increased during lactic acid fermentation by 16–50%, depending on the oil added. The lowest increase (16%) was observed in the beverage containing 0.02% rosehip oil, whereas the highest (50%) occurred with 0.02% lemongrass oil. Interestingly, the addition of 0.01% eucalyptus oil resulted in no significant change in TPC.

The observed increase in phenolic content during lactic acid fermentation is consistent with previous reports, for example, in fig fruit juice fermented by lactic acid bacteria [25]. Moreover, according to Goranov et al. [8], the addition of raspberry seed oil led to an approximately 1.3-fold increase in TPC during static lactic acid fermentation of wort under static conditions. Such increases are commonly attributed to the release of bound phenolics, bioconversion of complex phenolics into simpler forms, or microbial synthesis of new phenolic derivatives by lactic acid bacteria [26]. However, in the present study, no clear correlation between oil concentration and TPC was found. For instance, the increase in total phenolic compounds during fermentation with rosehip oil was similar at 0.01% and 0.03% addition levels. The beverage containing 0.02% lemongrass oil exhibited the highest TPC both at the end of fermentation and in terms of percent increase. For eucalyptus oil, the beverage with 0.02% addition showed the highest TPC, whereas 0.01% resulted in the lowest. In summary, 0.01% and 0.03% rosehip oil, 0.02% and 0.03% lemongrass oil, and 0.02% eucalyptus oil all yielded final phenolic concentrations equal to or higher than the control (Figure 1). A similar trend was reported by Trendafilova et al. [4], who investigated the production of lactic acid wort-based beverages with the addition of 0.025% and 0.05% (v/v) mint essential oil. The highest concentration of TPC was measured in the beverage with 0.025% mint essential oil.

Phenolic acids contribute to certain organoleptic properties, such as sour and bitter flavors. However, their primary medicinal significance lies in their antioxidant and antiradical activities, which arise from their chemical structure [27]. The results for phenolic acids are presented in Figure 2. Similar to the trend observed for total phenolic compounds (Figure 1), the concentration of phenolic acids increased during lactic acid fermentation in all variants except the one containing 0.01% eucalyptus oil. The increase can be explained with the hydrolytic enzymes of LAB, which are capable of releasing bound phenolic acids from esterified or glycosylated complexes [26]. Again, no correlation was found between the oil concentration and the phenolic acid content. The addition of rosehip oil resulted in similar phenolic acid concentrations in beverages containing 0.01% and 0.03% oil. The highest phenolic acid concentration was observed in the beverage supplemented with 0.02% lemongrass oil. Interestingly, the beverage with 0.01% eucalyptus oil was the only variant that showed a decrease in phenolic acid content during lactic acid fermentation. Moreover, at the beginning of fermentation, this variant exhibited the highest initial phenolic acid concentration.

Flavonoids are particularly beneficial bioactive compounds, acting as antioxidants and providing protection against cardiovascular diseases, certain types of cancer, and age-related degeneration of cellular components [28]. Changes in flavonoid content during fermentation depended on both the type and concentration of the added oil (Figure 3). The control sample, the beverage with 0.02% lemongrass oil, and those with 0.01% and 0.02% eucalyptus oil exhibited significant differences in flavonoid concentration between the beginning and the end of fermentation. However, a decline in flavonoid concentration was measured only in the beverage containing 0.01% eucalyptus oil. Across all formulations, the flavonoid content ranged between 112 mg/L and 129 mg/L quercetin equivalents.

Lactic acid bacteria (LAB) strains possess β-glucosidase enzymes that play a pivotal role in hydrolyzing flavonoid conjugates during fermentation, thereby influencing the bioavailability of polyphenols. The distinct metabolic behavior observed in the beverage containing 0.01% eucalyptus oil may be attributed to the inhibitory effects of the oil’s bioactive components on LAB activity, which could suppress β-glucosidase production or activity. Consequently, reduced enzymatic hydrolysis may have limited the release of flavonoid aglycones, leading to the observed decrease in total flavonoid content. Alternatively, the unique adaptability and enzymatic capacity of the LAB strain under varying oil concentrations may also contribute to differential transformation of phenolic compounds during fermentation [29].

3.3. Effect of the Oil Addition on the Antioxidant Activity (AOA)

Many factors, such as structural properties, temperature, the characteristics of the substrate susceptible to oxidization, concentration, and the presence of synergistic and pro-oxidant compounds and the physical state of the system, influence the efficacy of antioxidants. Therefore, a single antioxidant property model cannot fully reflect the antioxidant capacity of all samples [30]. Consequently, two antioxidant activity assays were selected to reflect the mechanisms of antioxidant action: the cupric reducing antioxidant capacity (CUPRAC) and the ABTS radical scavenging activity. The results for the antioxidant activity, measured by the CUPRAC and the ABTS methods are shown in Figure 4 and Figure 5, respectively.

The results for the antioxidant activity, measured by CUPRAC, were very interesting: in some cases the antioxidant activity increased during lactic acid fermentation, in others, it did not change, and only the addition of 0.03% rosehip oil resulted in a decrease in the antioxidant activity. However, the addition of 0.02% rosehip, lemongrass, and eucalyptus oil resulted in the production of beverages with the highest antioxidant activity (Figure 4).

The antioxidant activity, measured by the ABTS method, decreased by between 14% (0.03% lemongrass oil) and 39% (0.03% rosehip oil) during the lactic acid fermentation, which was contradictory to the CUPRAC results (Figure 5). The decline in ABTS activity may be due to the oxidation and degradation of antioxidants, as well as synergistic and redox interactions among various substances [31]. Differences in antioxidant activity could also reflect changes in phenolic profiles caused by lactic acid fermentation and the specific contributions of individual phenol compounds to overall antioxidant capacity [32]. As comprehensive phenolic profiling and metabolomic analyses were beyond the scope of the present work, this was acknowledged as a limitation, and future studies are recommended to address these aspects.

3.4. Effect of Oil Addition on the Sensory Evaluation of the Beverages Produced

Consumer acceptance of lactic acid–fermented wort beverages is limited by their sour and wort-like flavor and aroma [33]. Hence, oil addition can be used as a tool for improvement not only of the beverages biological value, but also of their sensory profile. However, sometimes the oil addition improved the beverage flavor and aroma, but sometimes the beverage flavor and aroma were so strong that consumers did not like the beverages with oil addition. All the final beverages were subjected to sensory evaluation and the results are presented in Figure 6 and Figure 7. Figure 6a shows that the rosehip oil addition enhanced the wort aroma of the beverages produced but did not affect wort flavor. Figure 6b shows that the increase in the lemongrass oil concentration did not result in the highest marks for oil aroma and flavor as for the other beverages. Moreover, when 0.03% lemongrass oil was added, the beverage had wort flavor and aroma because of stuck lactic acid fermentation. The positive correlation between eucalyptus oil concentration and the intensity of beverage flavor and aroma is presented in Figure 6c. The beverages with higher eucalyptus oil concentrations were preferred by the panel. In order to evaluate the appropriate combination of oil and concentration, a total evaluation of the beverages was made and the results are presented on Figure 7. Lemongrass oil addition improved the lactic acid wort-based beverage sensory characteristics to the greatest extent because all the beverages with this oil received higher or equal score to the control. It can be attributed to citral (neral and geranial), which masks the acidic note of lactic fermentation and contributes a fresh citrus aroma [12]. Conversely, eucalyptol in eucalyptus oil imparted camphoraceous and medicinal notes that reduced acceptance, while rosehip oil added subtle fruity undertones but limited aroma intensity. These findings highlight the importance of balancing volatile composition and microbial metabolism to achieve optimal sensory perception in functional fermented beverages.

Although the specific mechanisms and literature comparisons are discussed within individual result sections, a broader synthesis shows that the effects observed here are consistent with earlier studies reporting that essential oils modulate LAB fermentation through mild membrane-associated stress and by altering phenolic biotransformation patterns [4,7,8,15,23,25]. Taken together, our findings align with established evidence that low oil concentrations influence LAB activity without suppressing functional viability, while simultaneously affecting phenolic release and antioxidant behavior as previously reported in other LAB-fermented matrices [25,31,32].

4. Conclusions

The essential and cold-pressed oils can be incorporated into non-alcoholic fermented beverages when used at concentrations that maintain LAB viability while providing desirable aroma attributes. Among the tested formulations, the addition of 0.02% lemongrass oil yielded the most balanced outcome, characterized by enhanced phenolic enrichment, high antioxidant capacity, and the most favorable sensory scores. The findings should be interpreted with several limitations: phenolic and antioxidant analyses were spectrophotometric and did not identify specific compounds, the sensory panel was small and trained, and only one LAB strain and wort formulation were examined. Future work should include detailed phenolic and volatile profiling, storage stability evaluation, and broader consumer sensory testing. Overall, the results indicate that botanical oils can function as dual-purpose ingredients—enhancing aroma while contributing to measurable chemical characteristics—when incorporated at levels that do not compromise LAB viability.