Changes in colour characteristics of fibre-incorporated reduced-calorie herbal Rasmalai during storage

Introduction

Milk is highly perishable in nature and needs conversion to various value-added products to preserve its nutritive quality and enhance the shelf life. The development of traditional Indian dairy products dates back to 6000 years. Rasmalai is a chhana and concentrated milk based traditional dairy product containing about 60% total solids including sugar as sweetening agent with extremely delicate texture and taste (Sharma, 2004) [10] . Chhana and concentrated milk are used as its base materials for its preparation. The flattened chhana patties or Rasmalai balls (Tikki) are dipped in concentrated sweetened milk before serving. The product has a mild sweet and rich creamy flavor (Rupom et al., 2025) [8] . Rapid urbanization has led to drastic changes in lifestyle which has caused various health related conditions and chronic diseases. Functional foods containing different bioactive compounds provide health benefits to the host along with the basic nutrition. Addition of herbs into dairy products not only provide preservative effects, but they also possess antiinflammatory, anticarcinogenic, antihypertensive properties due to presence of polyphenols, carotenoids, flavonoids, curcumins etc. (Maji et al., 2023) [5] . Preparation of dairy products using low calorie sweeteners, dietary fibres and other herbal concoctions like Tulasi and Ashwagandha, is the need of the hour. Replacing cane sugar with the sucralose and addition of dietary fibre is a right choice for diabetic and health-conscious people. The culinary herb Basil, (Ocimum tenuflorum) commonly known as Tulasi is native to India and other tropical regions of Asia, having been cultivated there for more than 5,000 years. It is a rich source of essential oils such as α-Pinene, β-Pinene, Methyl chavicol, 1,8 Cineole, Linalool, Ocimene, Borneol, Geraneol, B Caryphyllone, n-Cinnamate and Eugenol (Taie et al., 2010; Shahrajabian et al., 2020) [13,9] , phenolic components like Phenolic acids and flavonol-glycosides (Javanmardi et al., 2002; Kivilompolo & Hyötyläinen, 2007; Shahrajabian et al., 2020) [3,4,9] and anti-oxidants such as caffeic, vanillic, rosmarinic acids, quercetin, rutin, apigenin, chlorogenic and p-hydroxybenzoic (Teofilovic et al., 2017; Shahrajabian et al., 2020) [9] . Purported health benefits for Tulasi and other Ocimum species include relief of stress and treatment of respiratory, gastrointestinal, and kidney ailments, as well as blood disorders and skin and eye diseases.

Isabgol husk (Psyllium), an indigenous natural dietary fibre is particularly rich in alimentary fibres and mucilage. It consists of 85% water-soluble fibre; which is partly fermentable. It is popularly used as a bulk laxative and biological experiments have confirmed its cytoprotective action (Purohit and Rathore, 2019) [7] . Dietary supplementation with isabgol has been shown to lower blood cholesterol levels, and especially LDL cholesterol. It is popularly used as a therapeutic agent for the treatment of constipation, diarrhoea, irritable syndrome, diabetes, and hypercholesterolemia (Sharma, 2015) [11] . Ashwagandha (Withania somnifera L.), commonly known as 'Indian Winter cherry' or 'Indian Ginseng' is considered as one of the most important medicinal plant in Ayurvedic medicine. The root of Ashwagandha is regarded as a tonic, aphrodisiac, narcotic, diuretic, anthelmintic, astringent, thermogenic and stimulant (Singh et al., 2011) [12] . The biologically active chemical constituents include alkaloids, steroidal lactones and saponins (Mishra et al., 2000) [6] . Sitoindosides and acyl steryl glucosides in Ashwagandha are stress busters (Singh et al., 2011) [12] . Sugar act as a bulking agent in food products, which is also associated with negative effects on the health of the consumers. Therefore, alternatives like sucralose, saccharin and aspartame are used as substitutes for sugar. These nonnutritive sweeteners possess the high sweetness potency which impart negligible calorie and are required in low amount (Campos et al., 2024) [2] . Rasmalai manufactured by fortification of Tulasi, Ashwagandha and Isabgol not only increase medicinal and functional value of the product but addition of sucralose to it, also makes the product suitable for dietetic people. Substitution of sugar and preparing functional dairy product by addition of Tulasi, Ashwagandha and Isabgol, may likely affect the colour profile of the product and can change the consumer acceptance. This study highlights the effect of these adjuncts on colour characteristics of fibre incorporated reduced calorie herbal rasmalai during storage conditions. In view of the above, an attempt was made to study the colour characteristics of the fibre incorporated reduced calorie herbal rasmalai during storage at ambient (32 ± 1 °C) and refrigerated storage conditions (5 ± 1 °C).

Materials and Methods

Cow and Buffalo milk were procured from University Dairy Plant, KVASU, Mannuthy, Thrissur, Kerela. Other ingredients like Ashwagandha root powder, Tulasi leaves, Isabgol/Psyllium husk powder, suji, citric acid, sugar, nuts and saffron were purchased from local market. Analytical grade chemicals were procured from approved firms of KVASU.

Preparation of Fibre-Incorporated Reduced-Calorie Herbal Rasmalai

Fibre incorporated reduced calorie herbal rasmalai was prepared as per the standardized method given by Sharma (2004) [10] with slight modifications and Ambili et al. (2023) [1] .

Colour Analysis of Fibre Incorporated Reduced-Calorie Herbal Rasmalai

Colour of the Rasmalai samples and concentrated sweetened milk was measured by reflectance spectroscopy technique employing reflectance meter, colour flex (Hunter lab Miniscan XE plus Spectrocolorimeter, Virginia, USA) with geometry of diffuse/8° (sphere-8 mm view) and an illuminant of D65/10°. Before the test, the instrument was calibrated with standard black glass and white tile as specified by the manufacturer. The light source was dual beam xenon flash lamp. Data were received from the software in terms of L* [Lightness, ranges 0 (black) to 100 (White)], a* [Redness, ranges from + 60 (red) to-60 (green)], and b* [Yellowness, ranges from + 60 (yellow) to-60 (blue)] in values of the international colour system.

Statistical Analysis

The data collected from the preliminary analysis were statistically analysed using Kruscal Wallis test (SPSS). In case of storage studies, repeated measures ANOVA and Independent t-test was performed for comparing between the samples in each period. Data obtained from the sensory analysis was statistically analysed using Friedman's test followed by Wilcoxon Signed Rank test (SPSS version 22.0). Each experiment was conducted in three replications.

Result and Discussion

Table 1 and 2 depicts the colour characteristics of fibre incorporated reduced calorie herbal Rasmalai ball and concentrated sweetened milk, respectively. The control and treated samples were analysed statistically using independent t-test. The colour parameters are expressed in terms of L, a, b values and their test static obtained by comparing with the control is given in the table 1 and 2. When the colour characteristics of the rasmalai ball is considered, 'L' value, which indicates lightness intensity, was significantly higher (p < 0.05) for the control (74.68 ± 0.03). The 'a' value which is the measure of redness for rasmalai ball was 1.25 ± 0.01 while for control, it was 1.19 ± 0.02 at p < 0.05. The optimized herbal rasmalai ball had a 'b' value of 15.87 ± 0.04 at p < 0.05. Hence, there was a significant difference (p < 0.05) in the colour characteristics (L, a and b value) of control and treated samples. In table 2, the comparison of values of colour characteristics indicated that there is no significant difference (p > 0.05) between the control sweetened concentrated milk and reduced calorie sweetened concentrated milk. The variation in colour characteristics of herbal rasmalai in terms of L, a and b values during the ambient temperature storage (32 ± 1℃) and refrigerated temperature storage is depicted in the table 3 and table 4, respectively. When samples were stored at ambient temperature (32 ± 1℃), L, a and b values were non-significant for control and herbal rasmalai. The mean L value of control increased from 76.44 to 83.44 and that of herbal rasmalai from 74.91 to 82.41 within 6 days of storage (table 2). When 'a' value was considered, the 'a' value of control decreased from 2.83 to 1.60 and similar decrease was observed in case of herbal rasmalai from 2.62 to 1.71 which may be due to the long-time soaking in the sweetened concentrated milk as the storage period increased. The b value of control varied from 18.88 to 19.58 and that of herbal rasmalai from 18.27 to 20.16. The table indicated that refrigerated storage had no significant effect on b value of control rasmalai. The F values of control for the terms L, a and b were 58.58, 23.35 and 1.591 respectively. The F values of herbal rasmalai for the terms, L a and b were 49.330, 5.886 and 24.051, respectively. Yikmis et al., 2020 [15] analysed the colour characteristics of functional sirkencubin syrup with purple basil during the refrigerated storage and reported non-significant difference between the control and developed product in terms of all colour parameters. He observed decrease in the value of L, a and b during the storage and explained that it may be due to anthocyanin degradation and the formation of maillard reaction products. These findings are contradictory to our findings.

Conclusion

It was concluded that there was a significant (p < 0.05) difference between the colour parameters i.e., L, a and b values of control and herbal rasmalai samples when kept at ambient (32 ± 1 °C) and refrigerated (5 ± 1 °C) storage temperatures. It was also observed that the control and herbal rasmalai balls had a significant difference in their colour parameters but no significant difference (p>0.05) was observed between control concentrated sweetened milk and reduced calorie concentrated sweetened milk samples.

Acknowledgement

AcknowledgementThe authors would like to acknowledge the support extended by Department of Dairy Technology, Verghese Kurien Institute of Dairy and Food Technology, Kerala Veterinary and Animal Sciences University, Mannuthy, Thrissur to carry out the present study.

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