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Mandatory assignment-lab-report

laboratory scientific report
Academic year: 2022/2023
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Name: Necka Earl D. Amolo Schedule: MW (4:00-7:00 PM) Date: February 09, 2023 Score:

Laboratory Report for Exercise No. 1 YEASTS AND MOLDS IN FOOD

Abstract

Yeasts and molds are two forms of fungus that contribute to food spoilage. Fungal spoilage of food remains a serious issue, accounting for between 5% and 10% of all losses in global food production. Despite this, methods for detecting, and especially identifying, food spoilage yeasts and moulds have advanced relatively slowly in comparison to methods for bacteria. This report investigates what genera present in isolated yeasts and molds by characterizing the morphology of the isolated sample. Findings suggest that the genus present in mold is Rhizopus. Which are known and common in decaying materials, including fruits and vegetables. Furthermore, in yeast, the genus found in the sample is Saccharomyces, particularly Saccharomyces cerevisiae.

Introduction

Numerous hundred species make up the broad and varied group of tiny food- borne fungus (yeasts and molds). Similar to how mold can develop on practically every sort of food at any moment, they are able to invade and spread on virtually any form of food. Grains, meat, and milk, fruits, vegetables, nuts, and fats are just a few examples. The growth of mold may cause a variety of food spoilages, including the development of pathogenic or allergic propagules and off-flavors, toxins, coloring, and rotting (Alegbeleye et al., 2022). Mold colonies can be nearly any color, but they are frequently big, dark blue or nearly black, with fuzzy borders.

Yeasts, on the other hand, are single-celled tiny creatures that are longer than bacteria and have morphologies like ovals, elliptical, spheres, or rods. Some yeasts, primarily those in the genus Saccharomyces, play a significant role in the manufacture of wine, beer, and alcohol as well as the leavening of bread. Other yeasts, sometimes known as wild yeasts, can lead to food deterioration issues. Although most yeasts are not linked to foodborne illnesses, some of them can infect both people and animals (Perricone, 2017).

As their development ranges are wider than those of bacteria and can tolerate more extreme environmental conditions, yeasts and molds both produce varying degrees of food deterioration and decomposition. The majority of the time, they can develop at a wide range of pH values, from pH 2 to pH 9, a large range of temperatures, from 5°C to 55°C, and yeasts and molds can also grow at low water activity aw ≤ 0. (Racchi et al., 2020).

Objectives

The objectives of the exercise are the following:

  1. Characterize the morphology of the isolated yeasts and molds.

  2. To determine the genera of isolated yeasts and molds.

Materials and Methods

Activity 2: Preparation of mold sample

By the use of an inoculating loop, some mold mycelia and fruiting parts were transferred to a drop of lactophenol blue on a glass slide. It was then covered with a cover slip. The glass slide was then transferred in the microscope for examination. It was examined first in low-objective and then high-power objective. Photos were then taken.

Activity 3: Preparation of yeast sample

In a test tube, a little quantity of dry instant yeast was poured. The test tube was filled with water to keep the yeast submerged, and it was then shaken to combine the ingredients. Then, smears of the yeast cultures were prepared on the glass slide that was stained with crystal violet. In order to make crystal violet, it was diluted with water in an Erlenmeyer flask until it turned blue. Before placing the yeast sample on the glass slide, one drop of crystal violet was added using a dropper, and the area was then covered with a cover slip after the yeast sample was placed. After that, it was examined with a low- and high-power objective, and pictures of it under the microscope were taken.

Table 2. Cultural and morphological examination of yeasts from the food sample Group Pigment Surface Growth

Shape Size Method of asexual reproductio n

Formation and number of ascospores

2 (Instant Dry Yeast)

Carotenoid/Yellow Rough, glistening

oval in shape

3-4 μm budding four or eight spores

According to the study of Zhang et al. (2018), S. cerevisiae (baker's yeast) is a major component of the microbial consortia of sourdough steamed bread and acts as a leavening agent by creating carbon dioxide through the alcoholic fermentation of carbohydrates, increasing the volume of the bread. Same process with the fermentation of wine by the presence of yeast that convert the sugar and will gradually produce carbon dioxide and alcohol.

Figure 1. Molds and yeast sample under microscope at 40x

Conclusion

By examining the data acquired through characterizing its morphology, the genus that is present in the molds sample is Rhizopus. Meanwhile, in yeasts, it is Saccharomyces, and its species is S. cerevisiae, which is the most used and researched yeast species.

Answers to Questions

  1. Differentiate the morphology of yeasts and molds.

Mold is multicellular. They emerge as multicolored mycelium or hyphae masses. They have the ability to reproduce both sexually and asexually. In comparison, yeast is unicellular and can be spherical, oval, or filamentous.

  1. What are the possible sources of yeasts and molds that contaminate the food sample? Elaborate.

Molds and yeasts can enter food from the air, water, and food ingredients. Molds, on the other hand, develop from tiny spores that float through the air. These spores turn into mold when they land on a piece of wet food. Although they don't really solely develop in water, they do so typically in areas with a lot of moisture. For example, molds may be present in the eating utensils we used that were stored in a moist environment, and these molds may have spread to the meal we consumed. Additionally, not only can they infect crops during storage and before harvest, but they can also do so in the field with grains, nuts, beans, and fruits. Yeasts can also invade crops. In relation to that, the primary sources of damaged yeast are raw materials, manufacturing facilities, as well as the previously mentioned air and water. Yeast have a crucial role in food and beverage degradation after contamination, notably in the transformation of fermented foods.

  1. What possible genera do the observed yeasts and molds from the food sample belong? Explain.

As stated above, yeast being observed is the Saccharomyces. It is just not as it is but based on its morphological characteristic of the food sample alone can distinguish and suggest that it is indeed a Saccharomyces. It was found out that these genera cells are round to ovoid, 5–10 μm in diameter and reproduce by budding and their surface growth can be rough and glistening. On the other hand, molds from the sample, the possible genera are the Rhyzopus. According to Petruzzello (2016) review, this genus forms filamentous, branching hyphae with no cross-walls (i., they are coenocytic). He also mentioned how Rhizopus reproduce by the formation of asexual and sexual spores. Sporangiospores are formed inside a spherical structure called the sporangium during asexual reproduction. The sporangiophore is a tall stalk supported by a massive apophysate columella. Sporangiophores are found among root-like rhizoids or connected with stolons (Petruzzello, 2016).

Appendices

Appendix A - Raw Data

Table 1. Interpretation of mold characteristic and determination of predominant genus Group Mycelium (septate/non- septate)

Asexual Spores Fruiting Heads

Size Color Shape

Special Structure (stolons, rhizoid, etc.)

1 (Carrots )

non-septate sporangiospores 2- 10 μm

blac k

conical- cylindric al

Foot cell, stolon, sexual spores

2 (String beans) non-septate sporangiospores 3- 6 μ m

blac k

Angular, subglobose and ellipsoidal

Stolon, foot cell, rhizoid

Table 2. Cultural and morphological examination of yeasts from the food sample Group Pigment Surface Growth

Shape Size Method of asexual reproductio n

Formation and number of ascospores

1 (Mauripan Instant Dry Yeast)

Carotenoid/Yell ow

dull oval in shape

3- μm

budding four or eight spores

1 (Apple Yeast)

none glistening Rod-like budding

2 (Mauripan Instant Dry Yeast)

violet dull, glistening

spherical 3- μm

fission four or eight spores

Figure 1. Molds and yeast sample under microscope at 40x of (Group 2)

Figure 2. Molds and yeast sample under microscope at 40x (Group 1)

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Mandatory assignment-lab-report

Course: Food Chemistry (FTC2)

University: Bukidnon State University

Was this document helpful?
Name: Necka Earl D. Amolo
Schedule: MW (4:00-7:00 PM)
Date: February 09, 2023
Score:
Laboratory Report for Exercise No. 1
YEASTS AND MOLDS IN FOOD
Abstract
Yeasts and molds are two forms of fungus that contribute to food spoilage.
Fungal spoilage of food remains a serious issue, accounting for between 5% and 10%
of all losses in global food production. Despite this, methods for detecting, and
especially identifying, food spoilage yeasts and moulds have advanced relatively slowly
in comparison to methods for bacteria. This report investigates what genera present in
isolated yeasts and molds by characterizing the morphology of the isolated sample.
Findings suggest that the genus present in mold is Rhizopus. Which are known and
common in decaying materials, including fruits and vegetables. Furthermore, in yeast,
the genus found in the sample is Saccharomyces, particularly Saccharomyces
cerevisiae.
Introduction
Numerous hundred species make up the broad and varied group of tiny food-
borne fungus (yeasts and molds). Similar to how mold can develop on practically every
sort of food at any moment, they are able to invade and spread on virtually any form of
food. Grains, meat, and milk, fruits, vegetables, nuts, and fats are just a few examples.
The growth of mold may cause a variety of food spoilages, including the development of
pathogenic or allergic propagules and off-flavors, toxins, coloring, and rotting
(Alegbeleye et al., 2022). Mold colonies can be nearly any color, but they are frequently
big, dark blue or nearly black, with fuzzy borders.
Yeasts, on the other hand, are single-celled tiny creatures that are longer than
bacteria and have morphologies like ovals, elliptical, spheres, or rods. Some yeasts,
primarily those in the genus Saccharomyces, play a significant role in the manufacture
of wine, beer, and alcohol as well as the leavening of bread. Other yeasts, sometimes
known as wild yeasts, can lead to food deterioration issues. Although most yeasts are
not linked to foodborne illnesses, some of them can infect both people and animals
(Perricone, 2017).

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