The effect of enrichment mint-flavored beverage with rice bran extract on physicochemical and rheological properties

Introduction: Food has historically been produced to provide nutrition and maintain health, and today the demand for functional food products is rapidly increasing. Functional drinks have become an integral part of the global beverage market, reflecting a trend towards health-conscious living in both developed and developing countries. These beverages offer health benefits beyond basic hydration, typically containing additives like vitamins, minerals, herbs, or bioactive compounds to support specific functions or improve health. This includes probiotic beverages, energy drinks, high protein drinks, meal replacement beverages, antioxidant-rich, fruit, and vegetable beverages. The market for these beverages has expanded dramatically, leading manufacturers to innovate and create diverse products that cater to these desires. The selection of active ingredients, production process, storage stability, as well as sensory properties of the developed functional beverage is important for consumer acceptability and market trend. Thus, functional beverages are a major focus of research and development in the functional foods sector. The mint family, or Lamiaceae, is one of the ten largest plant families worldwide, known for its aromatic plants and potential health benefits. Key members include peppermint, spearmint, and herbs like basil, thyme, and rosemary, which are popular in culinary traditions worldwide. This family contains various plant chemicals, such as monoterpenoids, triterpenoids, sesquiterpenoids, phytosterols, flavonoids, organic acids, lignins, glycosides, alcohols and aldehydes, each offering unique characteristics and benefits. The history of mint-flavored beverages dates back centuries, with early uses in medicinal tonics and herbal teas. Market trends indicate a growing demand for natural and organic mint flavors, as well as innovative combinations with other botanical ingredients.
The rice milling process produces valuable residues, mainly rice bran, used for oil extraction and as nutrient-rich byproducts. Often seen as waste, these byproducts contain dietary fibers, vitamins, and minerals that offer health benefits. Rice bran protein is a hypoallergenic, high-quality protein suitable for dietary supplementation, with byproducts comprising carbohydrates (16.1%-26.7%), fat (9.5%-22.9%), protein (13.2%-18.6%), and dietary fiber (20.5%-33.3%), predominantly insoluble fiber. The high content of antioxidants, including phenolics, flavonoids, and anthocyanins, contributes to its potent free radical scavenging activity.
Rice bran extract has gained attention as a valuable ingredient in beverage formulations due to its nutritional and functional properties. Faccin et al (2009) used rice bran to produce an organic drink. The obtained product was a suitable source of unsaturated fatty acids, minerals and essential amino acids. A study has shown that incorporating rice bran extract into the formulation of orange drink can result in a new functional beverage with higher nutritional value than regular orange juice (Raisi et al., 2012). Additionally, we can mention the production of a kiwi drink containing rice bran (Amiri et al., 2014) and the red grape drink enriched with rice bran extract (Raisi et al., 2013). The addition of rice bran extract to beverages can significantly impact their nutritional profile, potentially increasing protein content and phenolic compounds (Nisa et al., 2020). In another study, the impact of rice bran extract (0%, 5%, 10%, and 15%) and honey on the microbial, chemical, and sensory properties of a probiotic drink was examined. The results indicated that incorporating these ingredients into a drink containing Lactobacillus casei could result in a high-quality beverage (Hatemi et al., 2021). The ability of rice bran to improve lipid profiles, manage blood glucose levels, and exhibit antioxidant and anticancer activities makes it an attractive addition to health-conscious beverage formulations. On the other hand, incorporating these byproducts into food products promotes sustainability by minimizing waste. This research aims to explore the effectiveness of adding rice bran extract to mint-flavored beverages and assess its physicochemical and rheological properties for a functional product development.

Methods and materials:
Rice bran extract
To incorporate rice bran extract into the mint-flavored drink, Hashemi rice bran from Giltaz Gilan Company was used. The method of extraction can significantly influence the composition and properties of rice bran extract. Among the various new green extraction and separation technologies developed recently, subcritical water extraction is the most suitable that was used in this study. For this aim, the extract was obtained by treating the rice bran with subcritical water at 120 degrees Celsius for 15 minutes in an autoclave (Mac-5500 model, EYELA company, Japan). The rice bran was mixed with water at a 20% weight/volume ratio and placed in an Erlenmeyer flask before autoclaving. After the desired time, the bran is separated from the extract. The contents of the Erlenmeyer flask are poured into test tubes, and scum is removed using a Gerber centrifuge (Nova-safety 3670-4992 model, Gerber Company, Germany). Remaining particles are then separated by centrifuging the extract in test tubes (EBA 8s, Hettich model, Germany) at 4000 rpm for 20 minutes in three steps. The clear extract is stored in the refrigerator.
Preparation of mint flavored beverage using rice bran extract
The control sample consisted of mint extract (4% weight/volume), sugar (8.5% weight/volume), and citric acid (0.1% weight/volume), with water as the remaining volume. Treatments replaced 5%, 10%, 15%, and 20% of the water with rice bran extract, while maintaining the ratio of mint extract, sugar, and citric acid. Pectin gum (0.1%) was added for uniformity and to prevent phase separation. Samples were pasteurized at 85 degrees Celsius for 20 minutes using a bain-marie (model DIN EN 60629-IP20, Memmert company, Germany) and stored in 200 ml glass bottles at 4 degrees Celsius for three months.
Measurement
After preparing the beverages, their physicochemical (pH, brix, special weight, dry matter, ash, and turbidity) and rheological properties were analyzed. Specific gravity was measured with a pycnometer following Iranian national standard No. 2685, while ash, brix, and dry matter were assessed according to the same standard. Turbidity was assessed using reference tubes according to the national standard of Iran (No. 21449-2). pH was measured using a pH meter (Metrohm model 827 pH lab, Switzerland), and rheological characteristics were determined using a rheometer with a 26.65 mm cylindrical spindle (RheolabQC model, Anton Paar company, Germany). All conditions were replicated 3 times in a completely randomized design. Results were analyzed using ANOVA with SPSS software, and significance (p < 0.05) among samples treatments was assessed with Duncan’s Test.
Results and Discussion: The results showed that with an increase in the percentage of rice bran extract, the specific gravity (from 1.028 to 1.032 g/cm³), dry matter (from 7.86% to 8.82%), turbidity (from 80.33 to 550.33 NTU), and ash content (from 0.03% to 0.16%) increased; However, the average brix value remained unchanged (8.5%), below the permissible range (≥11) of Iranian national standard No. 23107. The average pH levels in the 10%, 15%, and 20% rice bran extract were significantly higher (p < 0.05) than in the control and 5% rice bran extract groups, which could be due to the presence of buffer compounds in the rice bran extract. A 20% increase in rice bran extract did not significantly affect pH, remaining within Iranian national standards. The effects of rice bran extract on the physicochemical properties of beverages, such as pH, acidity, soluble solids content, and sensory attributes, have been observed in previous studies (Faccin et al., 2009; Hatami et al., 2021). Amiri et al. (2014) reported that all physicochemical properties, including protein, dry matter, fat, and carbohydrate percentages, were higher in the rice bran-enriched kiwi beverage than in the control. The highest consistency coefficient was found in the 10% rice bran extract sample (0.0037±0.0001 mPa·s), while viscosity remained unchanged with increased extract percentages. The addition of rice bran extract altered shear stress and viscosity ratios in mint beverages, with R² values ranging from 0.81 to 0.99, indicating a strong model fit. The 15% rice bran extract sample had the highest R², while the control had the lowest. The 15% rice bran extract was identified as ideal for a mint-flavored drink. Raisi et al. (2012) noted that increasing rice bran extract decreased the consistency coefficient and increased the flow index in red grape beverages. Additionally, the rheological properties of rice bran-enriched products have shown interesting results, with changes in viscosity and flow behavior (Faccin et al., 2009; Schmidt et al., 2014).
Conclusion: Based on the results, rice bran extract is a suitable additive for a functional mint-flavored beverage, exhibiting favorable physicochemical and rheological properties, making it commercially viable for producing fortified, healthy drinks in the food industry. To enhance product quality, we recommend using other extraction techniques such as ultrasonication to improve transparency and reduce turbidity, ensuring a visually appealing, high-quality product that meets consumer standards.
Keywords: rice bran extract, mint flavored drink, physicochemical properties, rheological properties