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Inhibiting Flat Sour Bacteria In RTD Coffee

SPOILAGE – A Big Problem of canned and PET bottled long life coffee and tea milk beverages

Thermophilic spore-forming bacteria are the culprits in spoilage of canned or bottled milk coffees.

While heat treatment is effective in killing some of the bacteria, others which are highly resistant to heat (present even above 121 degrees Celsius), will grow flat sour bacteria and cause spoilage.

Mono-palmitic Ryoto Sugar Esters have been tested to effectively inhibit the growth of thermophilic bacteria.

Worried About Bacterial Spoilage In Hot Canned Drinks?

Recently in Japan, various canned drinks have been distributed through vending machines at 50-60.

The growth of naturally thermophilic heat-resistant spore forming bacteria such as flat sour bacteria has raised questions on the shelf life quality of canned drinks.

It has been found that Ryoto Sugar Esters have an excellent effect for inhibiting the growth of such bacteria, and they have come to be used widely as an antibacterial agent.

Ryoto Sugar esters are effective for Bacillus stearothermophilus, Bacillus coagulans, Desulfotomaculm nigrificans, or typical anaerobic spore forming bacteria of various members of Clostridium and have the interesting characteristic that the higher the heat resistance of the bacterium is, the smaller the amount of sugar ester required to have an effect.

This data shows the samples of spoiled milk coffee cans manufactured using commercial milk coffee products. D. nigrificans is used as the spoilage bacteria. Different amounts of sugar ester (Ryoto Sugar Ester P-1570) were added and left for 3 weeks at 55.

Effect of P-1570 on canned milk coffee drinks containing D. nigrificans
ContentSterilization conditionsSucrose fatty acid ester (%)Spoiled can/Number of sampled can
Milk
coffee
(250g can)
120
20 minutes
(Fo-16)



123, 25 min.
(Fo-40)
125, 25 min.
(Fo-60)
125, 45 min.
(Fo-100)
0
0.01
0.02
0.03
0.05
0.1
0

0

0
20/20
6/20
0/20
0/20
0/20
0/20
20/20

20/20

20/20
Data from Mitsubishi Chemical Corporation official website

Thus about 200 ppm of Ryoto sucrose palmitate can prevent the spoilage of canned milk coffee sterilized at Fo-16.

The relationship between the inhibition of spoilage in the presence of sugar ester (Sugar Ester P-1570) and without is shown. This coffee contains Clostridium thermoaceticum.

Relationship between the inhibition of spoilage in the presence of Ryoto P-1570 and the sterilization conditions

ContentSterilization conditionsSucrose fatty acid ester (%)Spoiled can/Number of sampled can
Milk
coffee
(250 can)
118, 20 min.
(Fo-10)
118, 20 min.
121, 30 min.
(Fo-30)
127, 25 min.
(Fo-100)
0.03

0
0

0
0/20

20/20
20/20

20/20
Milk
shake
118, 20 min.
(Fo-10)
118, 20 min.
121, 30 min.
(Fo-30)
127, 25 min.
(Fo-100)
0.03

0
0

0
0/20

20/20
20/20

20/20

It is clear that the sterilization condition, i.e. Fo value, can be lowered by the addition of 300 ppm of sugar ester.

If the Fo value could be lowered, the energy cost would be decreased

when manufacturing retort processed foods.

Products of higher quality can also be manufactured owing to the prevention of quality deterioration caused by high-temperature processing.

Ryoto Sugar Esters, especially palmitate (P-1570, P-1670) or myristate (M-1695) are effective in preventing the growth of C. botuliunm or Clostridium perfringens. Pic1 and Pic2 show the effect of Sugar Ester M-1695 on the germination of spores of C. botulinum in TPYG medium.

Pic. 1 – Effect of M-1695 on the germination of spores of C.botulinum 62A in the thiotone medium.
Incubation temperature was 370c

symbols:
o,control:>,M-1695 100-1000 ppm.

Pic. 2 – Effect of M-1695 on the germination of spores of C.botulinum type E Iwanai in the thiotone medium.
Incubation temperature was 37

Symbols are the same as legend to Pic1.

It is shown that Ryoto Sugar Ester M-1695 effectively inhibits the growth after germination of C.botulinum type A and type E.

Pic3 shows the effect of Sugar Ester P-1695 on the growth of spores of C.perfringens in chicken soup containing 50-400 ppm of P-1695 maintained at 37 after incubation.

Pic. 3 Effect of increasing levels of P-1695 on the growth from spores of C.perfringens type A NCTC 8238 in the chicken soup.
Incubation temperature was 37.

When 100-400 ppm of Ryoto Sugar Ester P-1695 was added, no growth of C. perfringens was observed and the number of living bacteria decreased.


These effects of Ryoto Sugar Ester for inhibiting the growth of heat-resistant spore-forming bacteria are utilized in various canned drinks sold through hot vending machines.

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