## 12 Survival of Probiotics in Yogurt  
Several studies have examined survival of probiotics in yogurt. Gilliland and Speck [397] reported that _L. acidophilus_ does not survive well in yogurt during storage, probably because of hydrogen peroxide produced by _L. bulgaricus_. Ng et al. [398] concluded that the reason that counts of some strains of _L. acidophilus_ decrease in the presence of _L. bulgaricus_ \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Functional Ingredi Category (in Bold) and Ingredient** & **Concentration** & **Effect on Properties** & **Ref.** \\ \hline
**Cyanobacterium** & & & \\ \hline Spirulina (a biomass of cyanobacterium) & 1 g per liter of yogurt mix. & This yogurt was less acidic than the control & \\  & 1 g per liter of yogurt mix. & yogurt on the 7 th day, and there was higher growth of lactic acid bacteria in this yogurt than for the control yogurt on the 7 th day. & [386] \\ \hline \hline \end{tabular}  
* RS2 is high amylose corn starch while RS3 is physically modified corn starch. 2 Inulin chain lengths were short (P95), medium (GR), and long (HP).  
\end{table} 
Table 5: Cont. is not due to the low pH, as these strains of _L. acidophilus_ can survive in a similar pH yogurt that was produced by glucono-delta-lactone. (Glucono-delta-lactone gradually releases gluconic acid at a comparable rate to acids produced by starter cultures.) Similar to Gilliland and Speck [397], Ng et al. [398] also suggested that this inhibition of some strains of _L. acidophilus_ may have been caused by high concentrations of hydrogen peroxide produced by _L. bulgaricus_. Shah et al. [399] obtained five brands of commercial probioticyogurt and determined how counts of _L. acidophilus_ and _B. bifidum_ changed over 5 weeks of refrigerated storage. Initial viable _L. acidophilus_ counts were in the range of 10\({}^{7}\) to 10\({}^{8}\) cfu/g for three of the brands, around 10\({}^{6}\) cfu/g for another brand, and around 10\({}^{4}\) cfu/g for the final brand, and the three brands with the highest counts maintained their counts better than the two brands with lower initial counts. Initial viable _B. bifidum_ counts were around 10\({}^{7}\) cfu/g for two brands and between 10\({}^{3}\) to 10\({}^{4}\) cfu/g for the remaining three brands, and all of these counts decreased during storage, especially during the latter stages [399]. Mani-Lopez et al. [400] reported that _L. acidophilus_ maintained better viability than _L. reuteri_ and _L. casei_ during storage of yogurt and fermented milk containing _S. thermophilus_. Hekmat et al. [401] used _Lactobacillus reuteri_ (now _Limosilactobacillus reuteri_) RC-14 and _Lactobacillus rhamnosus_ (now _Lacticaseibacillus rhamnosus_) GR-1 in the preparation of yogurt and found that _L. rhamn_'s GR-1 was surviving better than _L. reuteri_ RC-14. For _Limosilactobacillus mucosae_ CNPC007 incorporated into goat milk Greek-style yogurt, de Morais et al. [30] reported that counts decreased from 9.53 log cfu/g at 1 day of storage to 8.96 log cfu/g at day 28. Some factors may affect survival of probiotics in yogurt during storage. Kailasapathy et al. [402] manufactured fruit yogurts containing _L. acidophilus_ and _B. animalis_ ssp. _lactis_ and found that the fruit preparation usually did not decrease viability of these probiotics during storage compared to their plain yogurt controls. Ferdousi et al. [403] found faster declines of viable counts of various types of probiotics in yogurt stored at 20 \({}^{\circ}\)C compared to 5 \({}^{\circ}\)C, and _L. rhamn_'s HN001 maintained better viability than _B. animalis_ subsp. _lactis_ BB-12). Viability of probiotics in frozen yogurt has been reported in the literature. Hekmat and McMahon [404] manufactured frozen yogurt by fermenting an ice cream mix with _L. acidophilus_ and _B. bifidum_ before freezing and found decreases in counts from \(1.5\times 10^{8}\) cfu/mL to 4 \(\times\) 10\({}^{6}\) cfu/mL for _L.