Efeitos da aplicação de ultrassom de alta intensidade na produção de iogurte grego potencialmente probiótico

Abstract

The constant health concern has led consumers to seek functional foods such as yogurt, a fermented milk product obtained through the simultaneous action of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Greek yogurt differs in that it is made by partially removing whey, resulting in a firmer and creamier product. Yogurt is one of the vehicles for incorporating probiotics into the human diet, such as Lactobacillus acidophilus. Its consumption is associated with health benefits, including the regulation of intestinal disorders, reduced lactose intolerance, maintenance of cholesterol levels, and decreased carcinogenic, antimutagenic, and antihypertensive effects. One of the significant challenges in using probiotics is maintaining the viability of the culture during production, storage, and consumption. Ultrasound has proven to be a valuable tool in producing foods containing probiotics, and its application to yogurt raw materials may be associated with improved survival of these cultures in the final product. The study evaluated, through a full factorial design (2³) with three central points, the impact of ultrasound (20 kHz) considering pre-inoculation application time (1, 3, and 5 minutes), post-inoculation application time (0, 1.5, and 3 minutes), and power amplitude (20, 40, and 60%) on the textural and microbiological properties of Greek-style yogurt. During yogurt production, the ideal acidity was reached more quickly in samples subjected to longer ultrasound exposure times after inoculation and at the highest power amplitude value within the studied range, reducing fermentation time. During storage, the viability of the starter cultures and the probiotic met regulatory requirements, and the effects of the studied variables were not significant. Regarding the survival of Lactobacillus acidophilus in the in vitro digestive tract, the response surfaces indicated that the best results were obtained with high pre- and post-inoculation application times and intermediate power amplitude within the studied ranges, which may be due to the promotion of physiological resistance. In the texture profile analysis, only cohesiveness at 15 days showed significant negative effects due to the pre-inoculation application time and power amplitude; the other parameters (hardness, adhesiveness, springiness, and gumminess) remained stable throughout. Based on the results obtained, ultrasound application after inoculation for 3 minutes at 60% power amplitude is recommended for reducing fermentation time. Conversely, longer ultrasound application times (3 minutes) before and after inoculation, combined with intermediate amplitude, improve probiotic viability. In summary, ultrasound accelerated fermentation time and increased the resistance of probiotic cells without compromising microbial viability or the structural characteristics.