Effect of Pasteurization, Centrifugation and Additives on Quality of Concentrated Yogurt (Labneh)

A review of factors influencing the quality and sensory evaluation techniques applied to Greek yogurt

Greek yogurt is one of the fastest growing products in the dairy industry. It is also known as strained yogurt, which is obtained after draining the whey. As a result of the draining process, Greek yogurt has higher total solids and lower lactose than regular yogurt. Since it is a concentrated yogurt, its sensory characteristics are different from regular yogurt. However, there is little information about factors influencing the quality of Greek yogurt and sensory evaluation techniques applied to Greek yogurt. This review aims to describe the effects of ingredients, starter cultures, processing techniques and other parameters on quality characteristics and sensory properties of Greek yogurt. In addition, advantages and limitations of novel sensory evaluation techniques applied to Greek yogurt products are discussed. In particular, we take a look at advanced techniques such as the electronic nose and electronic tongue and the benefits of these techniques with regard to Greek yogurt. This review should help the Greek yogurt industry to improve its current products and develop innovative products based on appropriate food evaluation techniques.

Enhancement of Labneh Quality by Laser-Induced Modulation of Lactocaseibacillus casei NRRL B-1922

Labneh is positioned in the top ranking of the bestselling dairy products all over the world due to its health benefits and delicious taste. Labneh production depends mainly on probiotic bacteria in the fermentation of milk. Probiotic bacteria have many health benefits, which are driven by their selective bioactive metabolites that quantitively affect the fermentation products. The current investigation aimed to study the implementation of photobiomodulation through the irradiation of Lacticaseibacillus casei NRRL-B-1922 by a He–Ne laser (630 nm) with different laser doses (3, 6 & 12 J/cm2) prior to milk fermentation. This procedure sought to improve the probiotic bacteria’s activities while enhancing the labneh’s characteristics and consequently produce a more favorable labneh product with better marketing qualities. The photobiostimulated bacterial starter was found to induce increased titratable acidity with the moisture reduction of the labneh product under cold storage conditions for 20 days. The effect was most prominent when using a 12 J/cm2 laser dose. The flavor-aiding components, mainly diacetyl and acetaldehyde compounds, and sensory scores were increased in the labneh produced by irradiated L. casei when compared to the non-radiated probiotic culture after storing the products under cold conditions for 20 consecutive days. Moreover, the antioxidant and proteolytic activities of labneh produced by treated L. casei (12 J/cm2 laser dose) after cold storage were significantly elevated by 41 and 14%, respectively. In conclusion, we can report significantly improved selected characteristics in the final products after the employment of photobiomodulation process, the potential application of this concept on the industrial scale, and its implications on lengthening the product shelf life with improved qualities.

Fate of Listeria monocytogenes, Salmonella typhimurium DT104, and Escherichia coli O157:H7 in Labneh as a pre- and postfermentation contaminant

Commercially pasteurized milk (approximately 2% milkfat) was heated at 85 to 87 degrees C/30 min, inoculated to contain 2,000 to 6,000 CFU/ml of Listeria monocytogenes, Salmonella typhimurium DT104, or Escherichia coli O157:H7, cultured at 43 degrees C for 4 h with a 2.0% (wt/wt) commercial yogurt starter culture, stored 12 to 14 h at 6 degrees C, and centrifuged to obtain a Labneh-like product. Alternatively, traditional salted and unsalted Labneh was prepared using a 3.0% (wt/wt) starter culture inoculum, similarly inoculated after manufacture with the aforementioned pathogens, and stored at 6 degrees C and 20 degrees C. Throughout fermentation, Listeria populations remained unchanged, whereas numbers of Salmonella increased 0.33 to 0.47 logs during the first 2 h of fermentation and decreased thereafter. E. coli populations increased 0.46 to 1.19 logs during fermentation and remained that these levels during overnight cold storage. When unsalted and salted Labneh were inoculated after manufacture, Salmonella populations decreased >2 logs in all samples after 2 days, regardless of storage temperature, with the pathogen no longer detected in 4-day-old samples. Numbers of L. monocytogenes decreased from 2.48 to 3.70 to < 1.00 to 1.95 logs after 2 days with the pathogen persisting up to 15 days in one lot of salted/unsalted Labneh stored at 6 degrees C. E. coli O157:H7 populations decreased from 3.39 to 3.7 to < 1.00 to 2.08 logs during the first 2 days, with the pathogen no longer detected in any 4-day-old samples. Inactivation rates for all three pathogens in Labneh were unrelated to storage temperature or salt content. Unlike L. monocytogenes that persisted up to 15 days in Labneh, rapid inactivation of Salmonella typhimurium DT104 and E. coli O157:H7 suggests that these emerging foodborne pathogens are of less public health concern in traditional Labneh.

Resistance of yeast flora of labaneh to potassium sorbate and sodium benzoate

Ten yeast cultures belonging to eight species representing the yeast flora of labaneh were tested for their resistance to potassium sorbate and sodium benzoate. Changes in counts were monitored after 7, 14, and 21 d at 5 degrees C in yeast-free labaneh containing different concentrations of potassium sorbate or sodium benzoate. More than 400 mg/kg of sodium benzoate were needed to limit the counts of Saccharomyces cerevisiae (biovariants 1, 2, and 7) Cryptococcus curvatus, Pichia farinosa, Candida blankii, Debaryomyces hansenii, and Trichosporon brassicae to < or = 10(5) cfu/g after 14 d at 5 degrees C; 150 and 300 mg/kg were needed for Geotrichum candidum and Trichosporon cutaneum, respectively. When potassium sorbate was used, > 400 mg/kg were needed for P. farinosa and D. hansenii; 350 mg/kg were needed for S. cerevisiae biovar 1, Cr. curvatus, and C. blankii; 250 and 200 mg/kg were needed for S. cerevisiae biovariants 2 and 7, respectively; and < 100 mg/kg were needed for T. brassicae, T. cutaneum, and G. candidum. Less than 150 and < 250 mg/kg of potassium sorbate and sodium benzoate, respectively, were needed to limit yeast counts to < 10(5) cfu/g for 7 d at 5 degrees C in two commercial labaneh samples that had initial yeast counts of 4.8 x 10(2) and 9.0 x 10(2) cfu/g; 200 and > 400 mg/kg were required when the storage was extended to 14 d. In commercial labaneh with 9.6 x 10(3) cfu/g, > 300 and > 400 mg/kg of potassium sorbate and sodium benzoate, respectively, were needed to limit the yeast count to < or = 10(5) cfu/g after 7 and 14 d at 5 degrees C.