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European Journal of Applied Sciences – Vol. 12, No. 2
Publication Date: April 25, 2024
DOI:10.14738/aivp.122.12576
Amadou, N. M., Yam, S. A., Che, N. S., & Mathieu, B. (2024). Effect of Treatment on the Physicochemical, Microbial and Sensory
Properties of Tomato Powder. European Journal of Applied Sciences, Vol - 12(2). 135-143.
Services for Science and Education – United Kingdom
Effect of Treatment on the Physicochemical, Microbial and
Sensory Properties of Tomato Powder
Njoya Moyouwou Amadou
IRAD-Bambui; Food Technology and Post-Harvest Laboratory;
P.O. Box 51 Bamenda, Cameroon
Semi Aphonsius Yam
IRAD-Mankon. Nutrition Laboratory;
P.O. Box 125 Bamenda, Cameroon
Nde Sylvanus Che
IRAD-Bambui; Food Technology and Post-Harvest Laboratory;
P.O. Box 51 Bamenda, Cameroon
Barbi Mathieu
IRAD-Garoua; Food Technology and Post-Harvest Laboratory;
P.O. Box 415 Garoua, Cameroun
ABSTRACT
The purpose of this research aimed on the effect of various treatments on the
physicochemical, microbial and sensory properties of tomato powder. Fresh
tomatoes were pre-treated by sulphiting and blanching. After, they were dried
(40; 50 and 60 °C) and milled. 06 tomato powder samples were then obtained.
They were submitted to physicochemical (pH, titratable acidity, dry matter,
vitamin C and sugar), microbial (total bacterial, E. Coli and yeasts and mould) and
sensory (colour, aroma, acidity and overall acceptability) analyses. The taste,
colour, aroma, consistency and overall acceptability of tomato sauce prepared
from the most 03 acceptable tomato powder samples were also evaluated. The
vitamin C and sugar contents were not affected (p>0.05) by the treatment. The dry
matter reduced (p<0.05) at high temperature (60 °C) after blanching while no
effect was observed (p>0.05) by sulphiting. The pH was not affected (p>0.05) by
the pre-treatment method. However, blanching decreased the pH with the
increase of drying temperature although not significantly (p>0.05). At high
temperature, there was a non-significant (p>0.05) reduction of titratable acidity
after blanching in contrary to sulphiting where a significant increase (p<0.05) was
achieved at 60 °C. All the tomato powder samples were appreciated similarly
(p<0.05). The colour and the taste of the tomato powder sauce was not affected
(p>0.05) by the treatment. The most appreciated sauce in term of aroma,
consistency and overall acceptability was that from tomato powder blanched and
dried at 50 °C. Blanching and drying tomato at 50 °C could represent one of
appropriate methods for tomato powder production.
Keywords: Blanching; drying and sulphiting; fresh tomato; physicochemical, microbial
and sensory properties; tomato powder; tomato sauce.
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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 2, April-2024
INTRODUCTION
Fruits and vegetables are nutrients suppliers with positive effects on the wellbeing of the
human body. They are very important sources of vitamins and minerals. Also, they provide
many phytochemicals biologically active such as antioxidants and, are rich in fibres necessary
for the proper functioning of the body. They are then essentially considered as part of well- balanced diets [1, 2]. Tomato (Solanum lycopersicum) is a fruit classified as a legume, grown
throughout the warm, temperate and tropical regions of the world in general [3]. It is highly
cultivated in Cameroon and especially in the western highlands agro-ecological zone where it
represents a real income generating source. Studies have indicated the potential health
benefits of a diet rich in tomatoes [4]. Tomatoes can be consumed raw or as an ingredient in
many dishes like salads, sauces and drinks or cooked. Nevertheless, they are commonly
consumed fresh and over 80% of the tomato consumption comes from processed products
such as tomato juice, ketchup and sauce [4]. The advantage of using tomato products as food
ingredients is noticeable both to reduce environmental pollution and to provide an extra
income to producers [5]. Factors influencing the considerable increase in tomato
consumption include consumer awareness of benefits such as preventing cancer and chronic
diseases [6]. Tomato is a rich source of vitamins B and C, essential amino acids, sugar and
dietary fibres [1]. Regular consumption of tomatoes has been correlated with a reduce risk of
various types of cancers and heart diseases. These effects are attributed to the presence of
antioxidants, mainly carotenoids, ascorbic acid and phenolic compounds [7, 8]. Lycopene is
the most abundant carotenoid and the principal pigment found in tomato and, it is
responsible for its red colour [9]. Its presence stimulated research activities on fresh
tomatoes and tomato products [10]. Diets rich in lycopene should be promoted against risk of
chronic diseases [11, 12] including different types of cancers [13] and cardiovascular diseases
[14]. Despite its benefit effects on human body, tomato is a perishable crop due to its high
water content. Perishability of tomato represents a great problem from producers especially
during harvesting season due to its short shelf-life and high post-harvest losses. Spoilage or
post-harvest loss of tomato is as a result of various factors including inadequate handling,
storage and, transportation and processing facilities [15, 16]. In fact, it is favoured by limited
processing or preservative techniques which contribute to render the tomato very cheap
when produced in large quantities with reduction of farmers’ profit. Therefore, post-harvest
loss of tomato affects its production with severe consequences on farm-dependent
household’s incomes and livelihoods [16]. Development of preservative methods for tomatoes
remains an important challenge especially in the area with limited storage facilities.
Preservative methods consist mainly on water removal. Low water content leads to a
reduction of water activity which induces growth retardation of spoilage microorganisms.
Moisture content of crops to a certain level slows down the bacterial, enzymes, and yeasts
effect [17]. In fact, bacteria, fungi and moulds responsible of spoilage and decay need water
for their growth and multiplication. The moisture affects the shelf-life of foods and
agricultural material by their microbial spoilage, oxidation and physical structure [15]. Drying
is an important technique to reduce moisture content from foods. Sun drying is the oldest and
traditionally drying method. It is nutritionally and microbiologically safe and can be used to
preserve tomatoes and other fruits and vegetables for off season use [18]. However, tomatoes
dried directly by sun are more durable but the end product is infested with dirt [2]. Oven
drying method was observed to be more efficient and have an ability that will make the
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137
Amadou, N. M., Yam, S. A., Che, N. S., & Mathieu, B. (2024). Effect of Treatment on the Physicochemical, Microbial and Sensory Properties of
Tomato Powder. European Journal of Applied Sciences, Vol - 12(2). 135-143.
URL: http://dx.doi.org/10.14738/aivp.122.12576
product durable. It leads to a product with good quality and high nutritional value when
compare to sun drying method [19]. During drying process, the quality of tomato such as
colour, texture, nutrient content characteristics of the dried tomato is affected [20, 21]. Dry
tomato or tomato powder can be used diversely and serve as fresh tomato or tomato products
substitute. It can also serve as ingredients during various preparations (pizzas, spicy dishes,
etc.). The aim of the present study was to study the effect of various treatments on the
physicochemical, microbial and sensory properties of tomato powder.
MATERIAL AND METHODS
Production of Tomato Powder
The fresh tomatoes were purchased at Bamenda Food market, North-West Region, Cameroon.
They were then brought at the Food Technology and Post-Harvest laboratory of IRAD-Bambui
for processing. After sorting, the fresh tomatoes were weighed and washed several times with
potable water (tap water). They were then sliced into pieces of 6-8 mm thickness prior to pre- treatment as indicated below:
• Sulphiting according to Akanbi et al. [22]: the sliced tomatoes were dipped at room
temperature during 06 min in a solution obtained by combining 0.1% of potassium
metabisulphite and 0.6% calcium chloride solutions.
• Blanching by dipping the sliced tomatoes in hot water at 80 °C for 3-5 min.
After pre-treatments, the mixture was drained and the pre-treated tomatoes dried at 40 °C, 50
°C and 60 °C in vacuum oven [22]. 06 samples were then obtained as can been seen in table 1
below. The dried tomato was then cooled in desiccator for 01 h, milled using a household
blender and packaged in a plastic bag. The tomato powder achieved was subjected to various
analyses.
Table 1: Dried tomato samples
Pre-treatment Sample Drying temperature (°C) Drying time (h)
Blanching A 40 72
B 50 40
C 60 26
Sulphiting D 40 72
E 50 40
F 60 26
Physicochemical Analyses
Physicochemical parameters analysed were pH by using a pH-meter; dry matter and ash
contents according to the standard AOAC methods [23]; titratable acidity (% citric acid) as
described by the standard AOAC methods [24]; vitamin C by redox titration using iodine with
starch as indicator and sugar content (° Brix) by dissolving 5 g of powder in 50 ml of distilled
water and using a refractometer.
Microbial Analyses
Microbial analyses consisted of determination of total bacterial count, E. Coli count and yeasts
and mould counts using, nutrient agar, eosin methylene blue (EMB) agar and Saboraud
dextrose agar respectively.