RELATIONSHIPS BETWEEN LIGHTTREATED CULTURES AND LACTOSA CONTENT IN YOGURT

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RELATIONSHIPS BETWEENLIGHT-TREATED CULTURES AND
LACTOSA CONTENT IN YOGURT

• Stijepic M.1, Solaja M.2, Durdevic Milosevic
  D.3,
• Topalic Trivunovic Lj.2
• 1High Medical School, Prijedor, Republic of
  Srpska,
• Bosnia and Herzegovina
• 2Faculty of Technology, University of Banja Luka,
  Stepe Stepanovica 73,
• Banja Luka, Republic of Srpska, Bosnia and
  Herzegovina
• 3 High School of Technology, Hajduk Veljkova
  10, Sabac, Serbia
• contact address
• E-mail dadadada_at_panet.co.yu

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INTRODUCTION

• The results reported in many articles indicate
  different effects of natural and artificial light
  on microbial growth and metabolic products.
• Many factors are included in biological effects
  of applied light upon the bacteria radiation
  dose, intensity, wavelength, and post irradiation
  incubation time... Same of them are germicidal
  action in UV region of spectrum, the recovering
  in dark condition, mutagenic effects, change in
  metabolic pathways

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INTRODUCTION cont.

• Lactose is sugar found in milk and milk products.
  
• Many adults have trouble digesting lactose and
  dairy products due to low levels of lactase
  enzyme needed to break down lactose in intestine.
  
• Yogurt fermentation produced growth benefit as
  compared to the milk from which it was made by
  reducing the lactose content and by supplying
  microbial lactase activity.

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MATERIALS AND METHODS

• In this study we compared the abilities of
  Lactobacillus delbrueckii subsp. bulgaricus and
  Streptococcus termophilus to decrease lactose
  content in milk after different light treatments.
  
• Each one of culture was treated by visible light,
  incoherent polarized light or kept in dark.

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(MATERIALS AND METHODS cont.)

• Bacteria
• Lactobacillus delbrueckii subsp. bulgaricus and
  Streptocuccus thermophilus as starter culture
  Yoghurt V1 Visbyvac Dip 5u (DANISCO CULTOR,
  Niebull, Germany)
• Media
• Sterilised milk 2,8 fat
• Analyser
• Ultra sound lactosa analyser LactoScan
  (Micotronic LTD, Made in Europe)

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(MATERIALS AND METHODS cont.)

• Source of incoherent polarized light
• Bioptron Compact III, Zepter, Swiss
• Technical characteristics of light
• - wavelength 400-2000 nm,
• - linear polarization gt95 ,
• - constant radiation dose 2,4 J/cm2 per minute

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(MATERIALS AND METHODS cont.)

• Treatments of bacteria
• Dark (30, 40, 50 and 60 minutes),
• Visible light (30, 40, 50 and 60 minutes),
• Incoherent polarized light Bioptron light
• (30, 40, 50 and 60 minutes)

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(MATERIALS AND METHODS cont.)

• Samples of milk were inoculated by culture
  different in kind of treatments and treatments
  duration
• Lactose content was measured by ultra sound
  analyzer in 60 samples of milk and 180 samples of
  fermented products

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(MATERIALS AND METHODS-cont.)

• Calculations and analysis data
• ANOVA
• Linear regression
• Logarithmic and polynomial curves

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RESULTS AND DISCUSION

• FP IPL30 fermented product, treatment 30
  minutes by incoherent polarized light
• FP D30 fermented product, treatment 30 minutes
  in dark
• FP VL30 fermented product, treatment 30 minutes
  by visible light
• Figure 1. Lactose content in milk and fermented
  products after 30 minutes treatments

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(RESULTS AND DISCUSION cont.)

• Figure 1. shows
• the range of lactose content depending of
  treatments
• 2,49-2,99 for FP IPL 2,55-2,91 for
  FP D 2,58- 2,81 for FP VL,
• Results of statistical analysis
• - no significant difference in lactose content
  after different treatments in duration 30 minutes
  (p0,05)

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(RESULTS AND DISCUSION cont.)

• FP IPL40 fermented product, treatment 40
  minutes by incoherent polarized light
• FP D40 fermented product, treatment 40 minutes
  in dark
• FP VL40 fermented product, treatment 40 minutes
  by visible light
• Figure 2. Lactose content in milk and fermented
  products after 40 minutes treatments

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(RESULTS AND DISCUSION cont.)

• Figure 2. shows
• - the range of lactose content depending of
  treatments
• 2,84-2,90 for FP IPL 2,85-2,88
  for FP D 2,84- 2,87 for FP VL.
• Results of statistical analysis
• significant difference in lactose content after
  different treatments in duration 40 minutes
  (plt0,01)
• significant difference in lactose content between
  30 and 40 minutes treatments (plt0,01).

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(RESULTS AND DISCUSION cont.)

• FP IPL50 fermented product, treatment 50
  minutes by incoherent polarized light
• FP D50 fermented product, treatment 50 minutes
  in dark
• FP VL50 fermented product, treatment 50 minutes
  by visible light
• Figure 3. Lactose content in milk and fermented
  products after 50 minutes treatments

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(RESULTS AND DISCUSION cont.)

• Figure 3. shows
• the range of lactose content depending of
  treatments
• 2,85-2,89 for FP IPL 2,80-2,85
  for FP D 2,83- 2,87 for FP VL.
• Results of statistical analysis
• significant difference in lactose content after
  different treatments in duration 50 minutes
  (plt0,01)
• significant difference in lactose content between
  30 and 50 minutes treatments (plt0,01).

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(RESULTS AND DISCUSION cont.)

• FP IPL60 fermented product, treatment 60 minutes
  by incoherent polarized light
• FP D60 fermented product, treatment 60 minutes
  in dark
• FP VL60 fermented product, treatment 60 minutes
  by visible light
• Figure 4. Lactose content in milk and fermented
  products after 60 minutes treatments

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(RESULTS AND DISCUSION cont.)

• Figure 4. shows
• the range of lactose content depending of
  treatments
• 2,84-2,86 for FP IPL
  2,82-2,85 for FP D 2,80- 2,84 for FP
  VL.
• Results of statistical analysis
• significant difference in lactose content after
  different treatments in duration 60 minutes
  (plt0,01)
• significant difference in lactose content between
  30 and 60 minutes treatments (plt0,01).

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(RESULTS AND DISCUSION cont.)

• Decreasing of lactose content in average was min.
  37,25 for FP IPL30, and max. 40,35 for FP VL20

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(RESULTS AND DISCUSION cont.)

• Figure 5.
• FP IPL fermented product, treatments by
  incoherent polarized light
• FP D fermented product, treatments by
  incoherent polarized light
• FP VL fermented product, treatments by visible
  light

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(RESULTS AND DISCUSION cont.)

• Diagrams of experimental results present a
  percent of decreasing lactose concentration as a
  logarithmic function of treatments duration or
  the irradiation dose in the case of incoherent
  polarized light (R2 0,9743).

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CONCLUSION

• Experimental results show
• ? decreasing of lactose concentration in range
  37,5 - 40,35 depending of the kind of treatment
  and treatments duration,
• ? significant differences in lactose
  concentration
• (p lt 0,01) after cultures treated 40, 50 and
  60 minutes depending of the kind of treatments,
• ? each one of treatments in duration 30 shows no
  significant difference in lactose concentration
• (p 0,05),

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(CONCLUSION cont.)

• ? significant difference in lactose content
  between 30 and 40 minutes treatments, 30 and 50
  minutes treatments, 30 and 60 minutes treatments
  (plt0,01).
• ? diagrams of experimental results present a
  percent of decreasing lactose concentration as a
  logarithmic function of the irradiation dose in
  the case of incoherent polarized light (R2
  0,9743).
• Keywords lactose, light, Lactobacillus
  delbrueckii subsp. bulgaricus, Streptococcus
  termophilus, yogurt