What nutritional role does carrot powder play in probiotic cheese?

By Tarun Sai LomteFeb 24 2023Reviewed by Aimee Molineux

In a recent study published in the Journal of Dairy Science, researchers evaluated the nutritional properties of carrot powder and its application as an ingredient in probiotic soft cheese.

Carrot is a nutritious root vegetable rich in minerals, phenolics, carotenoids, polyacetylenes, fiber, and ascorbic acid. Several studies have reported using carrot juice in the development of probiotic beverages. Lactobacillus and Bifidobacterium strains, which are generally recognized as safe, are used as functional dairy products.

Probiotic bacteria have been used in cheese making because they enhance texture, flavor, and shelf-life. Moreover, adding natural bioactive compounds to cheese could augment functional and nutritional characteristics.

About the study

In the present study, researchers assessed the functional and nutritional properties of carrot powder and examined its application as a functional ingredient in soft cheese. Carrot slices were steam blanched to inactivate peroxidase and pectinase and increase the bioavailability of β-carotene. Slices were dried and powdered.

Fresh buffalo milk was pasteurized and aliquoted into four portions. 5% Sodium chloride, 2% mix of Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis, 15% Bifidobacterium longum, and 1% Lactiplantibacillus plantarum ssp. plantarum. were added to the aliquots. The first portion served as a control, while others were supplemented with increasing concentrations (0.2%, 0.4%, and 0.6%) of carrot powder.

Rennet was added, and fermentation continued at 40 – 42 °C. Fat, total protein (TP), and moisture were determined in cheese samples and carrot powder. Carbohydrates, ash, crude fiber, and caloric value in carrot powder were estimated. The Kjeldahl method was used to determine salt, soluble nitrogen (SN), titratable acidity, and non-protein nitrogen (NPN) in cheese samples.

The mineral profile of samples was determined using spectrophotometry (phosphorus), inductively-coupled plasma emission spectrometry (zinc, iron, magnesium, and calcium), and flame photometry (potassium and sodium). Total carotenoids and total phenolics were estimated. The antioxidant activity of carrot powder was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay.

Gas chromatography-mass spectrometry was performed to analyze semi-volatile and volatile compounds. The carrot powder was evaluated for antimicrobial activity against Bacillus cereus, Micrococcus luteus, Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, and Escherichia coli. The total bacterial count (TBC) in cheese samples was determined several times.

Findings

Ash, TP, moisture, fat, and fiber in carrot powder were estimated at 4.8%, 8.25%, 4.5%, 2.75%, and 11.94%, respectively. The total carbohydrate content in the powder was 72.3%, and the caloric value was 346.8 kcal/100 g. Ascorbic acid, β-carotene, and total phenolic content in the carrot powder were 50 mg, 123 mg, and 203.6 mg per 100 g, respectively. The antioxidant activity of carrot powder was 64.45%.

The growth inhibition zones ranged from 7 to 10 mm. The maximum growth inhibition zone was observed for P. aeruginosa. Cheese yield ranged between 18.2% and 20.5%, lower than that of fresh soft cheese made using cow milk. Adding carrot powder significantly increased the yield. Cheese supplemented with 0.2% carrot powder showed better flavor, texture, color, and appearance after 28 days of ripening.

Nonetheless, there were no significant differences between cheese samples with varying concentrations of carrot powder, except for cheese with 0.6% carrot that exhibited poor appearance and color. The total protein content was the highest (31.26%) in cheese, with 0.6% carrot. SN content was lower at day 0 but increased after 28 days in all cheese samples.

Data suggested that carrot powder addition to cheese samples caused secondary proteolysis after 28 days, albeit the NPN content decreased with increasing carrot powder concentrations. The ripening extension index ranged between 25.41% and 36.56% at day 0 and increased much slower by day 28. The moisture content of cheese increased with the concentration of carrot powder. Likewise, cheese samples with carrot powder had lower fat content than the control.

However, fat content increased after 28 days in cheese samples supplemented with carrot powder. TBC increased during ripening; cheese with 0.4% or 0.6% carrot powder had lower TBC at day 0 than the control cheese. Bifidobacterium and lactic acid bacteria (LAB) species increased significantly during ripening, suggesting that carrot powder addition induced and maintained probiotic bacterial growth.

Conclusions

The findings revealed that carrot powder is a good source of minerals, phenolics, β-carotene, and flavonoids. Carrot powder enhanced the antioxidant and antimicrobial activity of probiotic cheese and promoted the growth of probiotic bacteria in cheese. Thus, it could be used as a potential prebiotic to augment the viability of probiotic bacteria in different food products.