Development of made‐in‐transit set culture yoghurt: effect of increasing the concentration of reconstituted skim milk as the milk base

Abstract

The fermentation time, yoghurt acidity expressed as lactic acid, starter culture growth, viscosity and firmness of made-in-transit (MIT) set culture yoghurt produced using different concentrations of reconstituted skim milk powder (SMP) from 12% to 20% (w ⁄ v) as the milk base were investigated. All milk base formulations were ultra-high temperature sterilised at 138°C for 6 s. The results revealed that increasing the SMP concentration increased the viscosity and firmness of MIT set culture yoghurt. At 20% SMP, viscosity and firmness were 4650.8 cP and 1.266 N, respectively. Fermentation of MIT set culture yoghurt with 20% SMP was observed to be faster than with the other conditions. The fermentation time for a medium containing from 14% to 20% SMP could be extended to 168 h, reaching a final pH of 4.50-4.37 and at the same time improving the texture of the MIT set culture yoghurt. The SMP concentration had no influence on the total viable counts of starter bacteria in the yoghurt. The texture of MIT set culture yoghurt may be improved by increasing the concentration of SMP.

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“…Sodini et al (2002) observed that a mixed culture of STLA produced a fermentation time of approximately 4 to 8 h compared with LA by itself which had a fermentation time of 8 to 13 h. In another study, Damin, Minowa, Alcantara, and Oliveira (2008) found the shortest fermentation time to reach pH 4.5 was obtained with milk fermented by S. thermophiles with L. bulgaricus (5.4 h), and that the fermentation time was longer time when S. thermophiles was co-cultured with Bifidobacterium lactis (8.3 h) and L. acidophilus (9.3 h); the differences between them were significant (p < 0.05). The combination of STLA was found to extend the yoghurt fermentation to 168 h when incubated at 25 o C compared to STLB (Nor-Khaizura et al, 2012). Probiotics tend to grow slowly in yoghurt milk base, do not compete well with many starter strains and the probiotics show poor stability during storage.…”

“…Caseins are insolubilized protein and begin to precipitate when the pH of milk is reduced to pH 4.6. The soluble portion at pH 4.6 is known as whey proteins consisting of albumins and globulins (Chandan & O'Rell, 2006).The total solids content of the milk base influences the yoghurt firmness (Penna, Converti, & De Oliveira, 2006;Tamime & Deeth, 1980;Nor-Khaizura et al, 2012). The milk base protein content (Tamime, Kalab, & Davies, 1984;Trachoo & Mistry, 1998) and protein type (Cho, Lucey, & Singh, 1999;Penna et al, 2006;Sodini, Remeuf, Haddad, & Georges, 2004;Tamime et al, 1984) are important factors in determining yoghurt texture.…”

“…Probiotic bacteria have a beneficial effect on intestinal function and promote good health (Sanders, 1999). Some probiotic bacteria are claimed to aid lactose digestion (Vesa et al, 1996), prevent travellers' diarrhoea (Oksanen et al, 1990) and enhance the immune activity (Meydani & Ha, 2000). Certain levels of probiotic bacteria are required for these functions.…”

Sensory Descriptive Profiling and Consumer Acceptance of Made-in-transit (MIT) Set Yoghurt

“…Soukoulis et al (2007) found yoghurt fortified with MPC produced a product with a better texture than that produced through the addition of whey protein. Isleten and Karagul-Yuceer (2006) and Nor-Khaizura et al (2012) reported that yogurts fortified with NaCN exhibited better physical and sensory properties than control yoghurts. Yoghurts made with other casein-based ingredients were found firmer, with less syneresis, than yoghurts that were fortified at the same protein level with whey protein-based ingredients (Modler et al, 1983).…”

“…Fortification of the skim milk base with milk protein concentrate (MPC) or sodium caseinate (NaCN) improves the firmness of yoghurt, and syneresis decreases as the protein content increases (Nor-Khaizura et al, 2012, Schkoda, Hechler, & Hinrichs, 2001. Soukoulis et al (2007) found yoghurt fortified with MPC produced a product with a better texture than that produced through the addition of whey protein.…”