Hygienic and Microbiological aspects of Ice Cream

Abstract

Ice cream, a milk based product, is an important commodity in the international trade as it is consumed globally. It may sometimes serve a good medium for the growth of many organisms. Some may be pathogenic to humans and others can cause the spoilage of the product. The potential microbial hazards found in ice cream can be introduced after the pasteurization through the addition of contaminated ingredients and improper handling procedures .Proper pasteurization of ice cream mix and hygienic handling and processing of mix following pasteurization are of pivotal significance to have a good quality of ice cream. In order to ensure safety, it is imperative that the public and the trade are advised to pay adequate attention on some key areas from the preparation to the consumption of ice cream. Moreover, emphasis is given on the introduction of HACCP in milk processing establishments from food safety point of view.

Full text

42 BEVERAGE & FOOD WORLD JULY 2012
This Paper is dedicated to Dr. V. Kurien, Father of India's White Revolution
who brought India on the top position in milk production.
Hygienic and Microbiological aspects
of Ice Cream
Mahendra Pal*, Sihin Tesfaye* and Sisay Weldegebriel**
*Department of Microbiology, Immunology, Epidemiology and Public Health, Faculty of Veterinary Medicine, Addis Ababa University, P.O. Box 34,Debre Zeit, Ethiopia
**Department of Microbiology and Public Health, College of Veterinary Medicine, Mekelle University, P.O.231, Mekelle, Ethiopia
Email : palmahendra2@gmail.com
ABSTRACT
Ice cream, a milk based product, is an important commodity
in the international trade as it is consumed globally. It may
sometimes serve a good medium for the growth of many
organisms. Some may be pathogenic to humans and others
can cause the spoilage of the product. The potential microbial
hazards found in ice cream can be introduced after the
pasteurization through the addition of contaminated ingredients
and improper handling procedures .Proper pasteurization of ice
cream mix and hygienic handling and processing of mix
following pasteurization are of pivotal significance to have a
good quality of ice cream. In order to ensure safety, it is
imperative that the public and the trade are advised to pay
adequate attention on some key areas from the preparation to
the consumption of ice cream. Moreover, emphasis is given on
the introduction of HACCP in milk processing establishments
from food safety point of view.
Key words: Consumer, Hygiene, Ice cream, Microbial hazard, Pasteurization, Safety
INTRODUCTION
Dairy industries in most part of the world use the milk of cow to
manufacture milk products. The milk from buffalo, goat, camel, sheep,
horse, zebra and reindeer etc. are also used. As Indians are very
fond of milk and milk products, a wide variety of milk products such
as butter (makkhan), paneer, channa, curd (dahi), lassi, khoa, cream,
dried milk, sweetened condensed milk, buttermilk, ice cream, kulfi,
rabri, khurchan, peda, kalakand, burfi, gulabjamun, rasmalai,
rasgulla, chum chum, shrikhand, basundi, ghee, cheese etc. are
manufactured and sold in the markets (Sherikar and Majee,2004).
Moreover, India is the largest producer and consumer of milk and
milk products in the world .The credit goes to Dr.Vergeese Kurien,
Father of India’s White Revolution, whose sincere and dedicated
efforts brought India to the first rank in milk production in the world.
Among several milk products, ice cream received wide popularity
and great acceptance as a highly nutritious food internationally.
Ice cream is a frozen dairy product with delicious taste and flavour
and is relished by both sex, and all age groups of every strata of
society, in all seasons and in all climatic zones of the world. It is a
milk product that is sold in soft and hard form. It contains a variety
of ingredients such as milk, cream, butter, sugar, fruits, nuts, egg,
chocolate, honey , coconut , gelatin , flavouring and colouring agents,
etc ( Eckles et al.,1979 ). Fruits, nuts, candies, syrup etc. are added
to ice cream for flavour enrichment. The fat percentage and SNF in
ice cream is 10 % and 11 %, respectively. Sugar may be added up to
15 % for sweetening. In order to prevent the ice crystal formation,
sodium alginate is added. Glyceromonosterate is used for foaminess.
The ice cream being a nutritious food serves as a good medium for
the microbial growth due to the high nutritive value, almost neutral
pH and long storage duration (Bell and Kyriakides, 1998). Some
microorganisms including Listeria monocytogenrs, Yersinia
enterocolitica, Salmonella can survive in food even at low
temperature (ICMSF,1996).For ice cream, L. monocytogenese is of
significant food safety concern worldwide (Bell and
Kyriakides,1998).The heat treatment by pasteurization can destroy
most of the specific pathogens that pose risk to public health.
However, the pathogenic organisms can still be introduced in the
food product after pasteurization through the contaminated
ingredients, unclean or poorly cleaned utensils, food handler and
faulty handling (Marshall, 1998). The presence of coliform in frozen
products such as ice cream is an indication of post-pasteurization
contamination. The objective of the present communication is to
describe the hygienic and microbiological aspects of ice cream.
MANUFACTURE OF ICE CREAM
The production of ice cream involves eight steps which are listed
as follows:
1. Mixing of ingredients
2. Pasteurization
3. Homogenization
4. Aging
5. Freezing
6. Packaging
7. Hardening
8. Storage
The pasteurization, freezing and hardening are the main steps to
inhibit the growth of organisms and eliminate the microbial hazards
of the products for food safety point of view (Anderson and Nielson,
1998). The temperature for pasteurization of ice cream is 70 oC for
10 to 30 minutes. The freezing must be performed as quickly as
possible to prevent the formation of ice crystals. For aging, the ice
cream mix is held in sterilized vats for 3 to 24 hours at 4oC. The
hardening is done at – 34 oC to maintain better quality of ice cream.
It is very important that ice cream should be kept at – 18 oC during
transport and also display. The aging and freezing at – 5 degree
centigrade are preferred in the vending machine at retail shop. The
pre-made ice cream mix should be supplied to retail outlet under
refrigeration of 7 oC. The low temperature of 7 oC of ice cream mix is
unfavourable to the multiplication of organisms (Potter and Hotchkiss,
1995: Marshall, 1998).
Microorganisms in Ice Cream
Several types of organisms are isolated from ice cream (Ikenebomeh
and Ogaguvia, 1993: Sherikar and Majee, 2004; Ojokoh, 2006). These
are classified as follows:
1. Bacteria : Alkaligenes, Bacillus cereus, B. subtilis, Brucella
abortus, B.melitensis, Cornybacterium diphteriae, Enterococcus
faecium, E.faecalis, Enterobacter aerogenese, E. liquefaciens ,
Escherichia coli, Klebsiella ,Micobacterium tuberculosis, Proteus,
Pseudomonas, Salmonella, Shigella, Staphylococcus aureus,
Streptococcus pyogenese, Vibrio.

43 BEVERAGE & FOOD WORLD JULY 2012
2. Moulds: Absidia, Alternaria, Aspergillus, Fusarium, Mucor,
Neurospora, Penicillium, Rhizopus.
3. Yeasts: Candida, Geotrichum, Rhodotorula, Saccharomyces.
Hygienic and Microbiologial Aspects
Commercially processed and homemade ice cream is implicated in
outbreaks of disease. Salmonella enteritidis contamination of ice
cream was associated with a 1994 multistate outbreak (Vought and
Tatini ,1998).Heat stable toxins of Staphylococcus aureus caused
food poisoning in two persons through the consumption of ice cream
( Pal,2012 ).The infection from the food handlers, contamination of
the mix and contamination of the utensils are some of the factors
that are responsible for the outbreaks of disease through ice cream.
It is pertinent to mention that if any disease producing pathogen gets
entry into ice cream, it may remain viable for years in the frozen
state
- The types of milk and milk products (raw milk, condensed milk,
dried milk, cream, butter etc.), quality of gelatin, nuts, fruits,
sugar, chocolate, colour, etc., sanitary level of equipments,
efficiency of pasteurization and health of workers may contribute
to the hygienic and microbiological aspects of ice cream.
According to the bacteriological standards as prescribed by
Bureau of Indian Standards (BIS) (1998), ice cream should
contain less than 90 coliform count per gram where as total
standard plate count should not exceed more than 2,50,000 per
gram.
- Fresh fruits, nuts, frozen fruits, dried fruits, canned fruits are
widely used in ice cream preparation. Yeasts and moulds are
the common contaminants of the fresh and frozen fruits which
can be treated with sulphur dioxide or methyl bromide to destroy
these organisms. Nuts should be examined for moulds and can
be sterilized by a mixture of ethylene oxide and carbon oxide at
the ratio of 2:8. Coconut should be checked for the presence of
Salmonella, and walnuts for the moulds and parasites.
- The milk and milk based ingredients used for ice cream
preparation must be of high microbiological quality. These
commodities should be examined for coliforms, yeasts, moulds,
psychrotrops and lipolytic bacteria. The condensed milk should
not have more than 500 bacteria i.e colony forming units (cfu)
and yeasts and mould counts more than 10 cfu per gram.
Maximum total bacterial count in dried milk should not exceed
over 50,000 cfu per gram and coliform should be absent.
- Sugar is contaminated with coliform, thermophilic, mesophilic,
fungi (moulds and yeasts) which gain entry during production
and storage. It is important to mention that the level of mesophilic
count and fungal count should not exceed more than 20 and 1,
respectively.
- The air can be a potential source of microbes in ice cream. Air
is incorporated for overrun. Overrun is a term used to describe
the increase in volume caused by whipping air into ice cream
mix during freezing process. The usual range of overrun in soft
ice cream is 40 % and hard ice cream is 70 to 100 % .If ice
cream has 100 % overrun, it has a volume of air equal to the
volume of mix. In other words, one liter of mix makes two liters
of frozen ice cream of 100 % overrun. Therefore, it is advisable
to use only the filtered air during the preparation of ice cream.
- Aqueous colour may increase microbial counts since it is added
after the pasteurization of ice cream mix. Hence, alcoholic and
dry colours are preferred. It is recommended to prepare aqueous
colour in properly boiled water and add in ice cream mix before
pasteurization.
- Packaging materials are reported to be the source of fungal
spores and hence, it is advised to effectively sanitize the
packaging materials before using to pack ice cream.
- The equipments and utensils at the selling center should be
kept in hygienic conditions.
- Since ice cream contains solids, there is heavy deposition on
the pasteurizer plates which may facilitate the growth of
microbes. Therefore, thermometer, pasteurizer plates, valves,
coolers etc should be properly cleaned and sanitized regularly
to avoid contamination.
- The presence of coliform in ice cream is chiefly due to
contamination from equipment which have not been cleaned and
sanitized properly after each production cycle. Hence, the plant
should be inspected regularly and microbial test should be
conducted periodically by using swab and rinse techniques.
- Sanitation is critical for ensuing that milk products do not get
recontaminated. As Listeria monocytogenes, a well known food
borne pathogen, needs moisture for growth, therefore, floors
should be kept drained of standing water and be kept as dry as
possible so that L. monocytogenese may not get the opportunity
to grow on floors.
- Food handlers with poor personal hygiene can be the potential
source of infection in milk industry as many pathogens have
been recovered from healthy as well as sick food handlers.
Staphylococcus aureus can come from the skin, nose hands
and clothes of the handler. Coughing, sneezing, talking produce
droplets which could settle on ice cream during transport, storage
and retailing. The presence of coliform in ice cream may be due
to post pasteurization contamination by handlers with poor
sanitary practices. The level of the presence of these organisms
in food has been described as index of food hygiene. It is,
therefore, imperative that education and training in good food
hygiene practices should be imparted to all food handling workers
(W.H.O., 1962; Schlundt et al., 2004; Pal, 2012).
- It is pertinent to mention that all the ingredients used in the
manufacturing of ice cream should be tested for total bacterial
count, coliform, moulds and yeasts, anaerobic bacterial count
and also for Salmonella and beta hemolytic streptococci.
It is concluded that hygienic and microbiological aspects must
be critically observed during the manufacture of ice cream. This
will certainly help to improve the quality, increase the self life
and ensure safety of the product besides reduce the incidence
of food poisoning outbreaks.
ACKNOWLEDGEMENTS
We are very grateful to Prof.Dr.Ram Krishan Narayan for going
through the manuscript and Dr.Man Mohan Keshav for sending us
some relevant literature on the subject.
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