Technological profile of traditional therapeutic acidophilus milk:

• Statement (I) is true: Lactobacillus acidophilus is a slow acid producer and competes poorly with other microorganisms. Therefore, traditional acidophilus milk production historically requires severely heated milk (autoclaved at $115^\circ\text{C}$ for 15-20 min or boiled thoroughly) to eliminate all competitors and release stimulatory peptides/sulfhydryl compounds, inoculated with a high starter dosage of $2\text{--}5\%$.
• Statement (II) is true: Severe heating generates pronounced Maillard and sulfhydryl cooked flavor, while high terminal acidity (titratable acidity $1.0\text{--}1.5\%$) imparts an astringent, medicinal tartness, making traditional acidophilus milk notoriously unpalatable compared to sweet acidophilus milk.

Commercial probiotic dairy products in the Indian market:

• USA features products like DanActive and Lifeway Kefir.
• Denmark features Gaio (Cultura).
• France features Actimel (Danone).
• 'Nutrifit' is a pioneering probiotic drink launched in India by Mother Dairy Fruit & Vegetable Pvt. Ltd. (NDDB). It was formulated with the well-documented human probiotic strain Lactobacillus acidophilus NCFM to enhance gut immunity and digestion in Indian consumers.

Physiological and genetic profile of the genus Bifidobacterium:

• Statement 1 is true: Bifidobacteria require complex carbohydrates (human milk oligosaccharides, prebiotics) and specific bifidogenic factors (N-acetylglucosamine-containing oligosaccharides) for optimal proliferation.
• Statement 2 is true: Bifidobacteria belong to the phylum Actinomycetota and possess a high genomic G+C content ranging between $55\%$ and $67\%$.
• Statement 3 is NOT true (incorrect): Bifidobacteria are strictly Gram-positive, CATALASE-NEGATIVE, non-motile, non-sporeforming, and NON-GAS PRODUCING bacteria. They ferment hexoses exclusively via the unique fructose-6-phosphate 'bifid shunt' without producing $CO_2$ gas.
• Statement 4 is true: Bifidobacterium infantis and B. bifidum constitute up to $90\%$ of the gut microbiota in healthy breast-fed infants.

Scientific definition and guidelines for probiotics (FAO/WHO):

• Statement 1 is true: Probiotic efficacy, immunological modulation, and health benefits are strictly strain-specific (e.g., Lactobacillus rhamnosus GG vs other L. rhamnosus strains).
• Statement 2 is true: Probiotics must survive food processing and maintain therapeutic minimum viable counts (typically $\ge 10^6\text{--}10^7\text{ cfu/g}$) until the end of shelf life.
• Statement 3 is true: Probiotic strains must have GRAS status and proven non-pathogenic, non-toxic safety profiles.
• Statement 4 is NOT true: Traditional yogurt starter organisms (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) lack acid and bile tolerance, cannot survive the gastric passage, and cannot adhere to or colonize human intestinal epithelial cells. Therefore, they do not qualify as true probiotics.