PAPER OF PROFESSION ENGLISH

PAPER OF PROFESSION ENGLISH

Effects of yogurt starter cultures on the survival of Lactobacillus acidophilus

By

Meta Aquarista Galia

1414051063

AGRICULTURAL PRODUCT TECHNOLOGY

AGRICULTURAL FACULTY

LAMPUNG UNIVERSITY

2015

ABSTRACT

Probiotics such as Lactobacillus acidophilus are generally used to provide health benefits to consumers through fermented milk products through out the world;, among yoghurt which is a popular product in the world. For realize most of the health benefits, the amount of viable probiotic cells must be delivered to the consumer when the consumer.  This study focused on the impact of yoghurt starter culture to the survival of the five strains of L. acidophilus, with an emphasis on low pH and acid production. The behavior of living differential between L. acidophilus strain further analyzed. the number of viable cells of L. acidophilus were determined during storage 4 ° C in various types of yogurt made with Streptococcus thermophilus, L. delbrueckii ssp. bulgaricus two species of starter cultures, or Glucono-delta-lactone (GDL). All types of yogurt, but yogurt pasteurization, which is co-fermented with L. acidophilus. Yogurt is the filtrate was analyzed for the presence of inhibitors and for the amount of hydrogen peroxide. Propagation of L. acidophilus is not affected by the starter culture for all strains reached high levels on day 0 of the storage period. In addition, the filtrate collected from yogurt is made with a starter culture proved to have higher inhibitory activity against L. acidophilus than that made with GDL. The presence of viable starter culture is needed to affect the survival of some strains, such as the pasteurized yogurt has no effect on their survival.

I.                   INTRODUCTION

Yogurt is one of the most popular fermented dairy products are commonly used as food vehicles to compounds, modulate host immune system, inhibit Helicobacter deliver probiotics to consumers. Yogurt is a fermented milk producted by lactic acid bacteria at a temperature of 37-45°C. Yogurt is very beneficial for the body, good for obtaining the nutritional value also providing health benefits, especially for digestion in which yogurt bacteria that enter will envelop the intestinal wall so that the wall of the intestine becomes acidic and this condition causes microbial pathogens can not proliferate. Yogurt can be defined as a food produced by culturing one or more of the optional dairy ingredients namely, cream, milk, partially skimmed milk, and skim milk, used alone or in combination with a characteristic bacterial culture that contains lactic acid producing bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus.

“Probiotics” are defined as “live microorganisms which when their viability in the products has been cited as an important administered in adequate amounts confer a health benefit on the prerequisite for achieving beneficial health effects (Galdeano and host” (FAO/WHO, 2001).For instance, Lactobacillus acidophilus, a common probiotic species can prevent or treat some gastrointestinal (GI) disorders (reviewed by WGO, 2008). Enhancing our understanding of L. acidophilus survivability in yogurts may provide a foundation to improving probiotic strains and/ or starter cultures, and subsequently lead to a more effective delivery of probiotic-associated health benefits via fermented dairy products.

II.                MATERIALS AND METHODS

2.1. Bacterial strains and culture media

There are two types of species containing S. thermophilus and L. delbrueckii ssp. bulgaricus, provided by Chr. Hansen (Milwaukee, WI) in the form of Direct Vat Set. This species is then isolated on MRS agar and incubation performed. After incubation at 37 ° C anaerobically for 48 hours, two different colony morphology were observed.

2.2 Production of different types of yogurt

The typical yogurt was made with the fermentation of both starter cultures (S. thermophilus and L. delbrueckii ssp. bulgaricus). Yogurts were also made with individual starter culture species. Finally, yogurts weremade without any starter cultures. 

2.3. Enumeration of L. acidophilus in yogurt

To determine cell count is using SPC, a conventional method. It was used to quantify viable L. acidophilus cells. Anaerobic incubation at 37 °C for 48–72 h, CFU/g was calculated. Relative survival for each strain was determined by dividing the CFU/g.

2.4 Preparation of yogurt filtrate

To study the effect of secretory metabolic products produced from starter cultures on probiotics, the survival of L. acidophilus NCFM was determined in MRS broth containing yogurt filtrate.

2.5 Determination of hydrogen peroxide content

An enzymatic method as described by Gilliland (1969) was used to measure the amount of H2O2 in yogurt on day 0. Owing to the high viscosity of yogurt, the measurement was made on diluted yogurt filtrate.

To analyze the differences of L. acidophilus survival among samples, two-way analysis of variance (ANOVA) was conducted using the General Linear Model in Minitab software version 15.1. One-way ANOVA was used to analyze the survival of L. acidophilus in various amounts of yogurt filtrate, and the amount of H2O2 produced by different samples. Statistical significance was defined as Pb>0.05.

III.             RESULTS AND DISCUSSION

3.1  Survival of L. acidophilus in the presence and absence of starter cultures

Viable cell counts of both NCFM and ATCC 700396 decreased drastically beginning on day 14. Their final mean viable cell count on day 28 were 1.3×10⁴ and 1.1×10⁵ CFU/g, respectively. Statistical analysis showed that the relative survival of L. acidophilus NCFM was significantly lowered than that of SBT2062, LA-5, and PIM703 (P<0.05).

3.2 L. acidophilus survival in the presence of individual starter culture species

The latter species had a stronger effect on L. acidophilus NCFM, which showed a mean 2.5-log reduction (4.0×10⁷ to 1.3×10⁵ CFU/g), compared to SBT2062 that only had 0.6-log reduction (7.1×10⁷ to 1.8×10⁷ CFU/g). A marginal significant difference was observed at P=0.0569. On the other hand, NCFM survived well in yogurts made with S. thermophilus alone (0.5log reduction) while SBT2062 had 100% survival.

3.3 Starter cultures metabolites and L. acidophilus survival

When known amounts of L. acidophilus NCFM and SBT2062 were added to pasteurized yogurts made with starter cultures or GDL, both strains showed steady survival with only a maximum of 0.15-log reduction (1.4×10⁷ to 9.9×10⁶ CFU/g) during a 15-day storage period for NCFM

This study aims to overcome the effects of the starter culture L. acidophilus and use a comparative approach to help understand the behavior observed differential between strains.

As with probiotics intrinsic activity, the behavior of the survival of L. acidophilus in yogurt during refrigerated storage period also shown a significant strain to strain variation. Although the growth of all strains of L. acidophilus examined was not affected, the survival of some strains clearly hampered by the presence of yoghurt starter culture. This study discusses how the starter culture L. acidophilus viability is affected, treatment without starter culture must be included for comparison.

IV.             CONCLUSION

To take advantage of the potential health benefits of probiotic L. acidophilus, they must be delivered at a high dose through foods such as yogurt. While many previous studies have reported that the accumulation of acid negatively affected their survival during refrigerated storage period, we showed low pH and/ or accumulation of organic acids does not always play an important role. Between two species starter culture, L. delbrueckii ssp. bulgaricus given a greater detrimental effect on the survival of some strains of L. acidophilus possible to produce inhibitory metabolites such as H2O2. Such as probiotics their intrinsic activity, viability of L. acidophilus in yogurt showed marked variations in strain-to-strain. Comparing strains with varying behaviors can lead to the identification of new factors associated with better survival, development strategy of processing or storage to improve the survival of probiotics, and further more effective delivery of health benefits through fermented milk products.

REFERENCES

Food, Agriculture Organization/World Health Organization (FAO/WHO), 2001. Health and nutritional properties of probiotics in food including powder milk with live lactic acid bacteria. Report of A Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties in Food Including Powder Milk with Live Lactic Acid Bacteria. Cordoba, Argentina.

Dave, R.I., Shah, N.P., 1998. Ingredient supplementation effects on viability of probiotic bacteria in yogurt. Journal of Dairy Science 81, 2804–2816.

Gilliland, S.E., 1969. Enzymatic determination of residual hydrogen peroxide in milk. Journal of Dairy Science 52, 321–324.

Lourens-Hattingh, A., Viljoen, B.C., 2001. Yoghurt as probiotic carrier food. International Dairy Journal 11, 1–17.