REVIEW
published: 15 June 2021
doi: 10.3389/fnut.2021.661693
Utilization of Vegetable and Fruit
By-products as Functional Ingredient
and Food
Ke Qi Lau, Mohd Redzwan Sabran* and Siti Raihanah Shafie
Department of Nutrition, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
With the constant growth of the human population, the global demand for food is
increasing annually. Food security is an arising issue due to decreased resources and
massive waste production from the agricultural sector. For example, not all parts of fruits
and vegetables are consumed by consumers, and this phenomenon can lead to huge
amounts of food wastes that are produced globally. Moreover, non-utilized agriculture
by-products, including seed coat, hull, husk, peels, seeds, and pomace, can cause
Edited by: environmental issues. Hence, efficiently utilizing food wastes, such as vegetable and
Juliana Morales-Castro, fruit by-products, could be a way to increase food sustainability, and in line with the
Durango Institute of
Technology, Mexico
United Nations Sustainable Development Goal (SDG) to ensure sustainable consumption
Reviewed by:
and production patterns. Moreover, certain agriculture by-products are reported to
Sapna Langyan, have a high nutritional value and could be potentially used as functional ingredient and
National Bureau of Plant Genetic food in the food industry. This review article summarizes findings on the development
Resources (ICAR), India
Diego A. Moreno, of new functional foods by utilizing different types of agriculture by-products, that
CEBAS-CSIC, Food Science and is, vegetable and fruit by-products as ingredients. Furthermore, the nutritional values,
Technology Department, Spanish
National Research Council, Spain
processing methods, product acceptability, and potential uses of these vegetable and
J. Fernando Ayala-Zavala, fruit by-products are also discussed. These by-products can be an alternative source of
Centro de Investigación en nutrients to support the global demand for functional foods and as one of the strategies
Alimentación y Desarrollo, Consejo
Nacional de Ciencia y Tecnología to cope with food insecurity. Studies have shown that different types of fruit and vegetable
(CONACYT), Mexico by-products were well-incorporated in the development of functional foods, such as
*Correspondence: bakery products and dairy products. Of great importance, this review article provides
Mohd Redzwan Sabran
an insight of the nutritional value, health benefits, and utilization of fruit and vegetable
by-products.
Specialty section:
Keywords: vegetable by-products, fruit by-products, food waste recovery, utilization of food waste, functional
This article was submitted to
food, health benefit, food security
Nutrition and Sustainable Diets,
a section of the journal
Frontiers in Nutrition
INTRODUCTION
Received: 31 January 2021
Accepted: 29 April 2021
In the agriculture field, postharvesting, processing, distribution, and consumption sectors could
Published: 15 June 2021
generate agriculture by-products that are wasted in huge amounts, which can contribute to the
Citation: food waste problem (1). These food wastes are part of unintentional and intentional losses, which
Lau KQ, Sabran MR and Shafie SR
can lead to wastage of agriculture by-products (2). The unintentional losses include inadequate
(2021) Utilization of Vegetable and
Fruit By-products as Functional
farming technologies and lack of proper transportation, whereas the intentional losses include due
Ingredient and Food. to human eating habits. Approximately 45% of fruits and vegetables are wasted worldwide, which
Front. Nutr. 8:661693. is one of the categories with the highest wastage rate (1). The highest agricultural wastage is found
doi: 10.3389/fnut.2021.661693 in Europe, Latin America, North America, and Oceania, and it accounted for ∼10% higher than
Frontiers in Nutrition | www.frontiersin.org 1 June 2021 | Volume 8 | Article 661693
, Lau et al. Vegetable and Fruit By-products
that of industrialized Asia (1). Moreover, the highest production in developing countries increases the global agricultural wastes.
wastage is found in Sub-Saharan Africa, which constitutes It is evident as organic wastes generate up to 80% of the total
∼20% (1). solid wastes in any form, whereas the manure production can
It is of great concern that a massive amount of agricultural by- reach up to 5.27 kg/day/1,000 kg live weight, on a wet weight
products contributes to the food waste problem, subsequently, basis (5). Agriculture by-products are also largely contributed
it can further lead to many environmental and economic issues by the improper utilization of fruits and vegetables that are
(1). According to FAO, food loss and waste is the second highest commonly overproduced seasonally (6). Vegetable and fruit by-
cause of greenhouse gas emission. Statistically, 1.3 billion tons products represent 44% of global food wastes by commodity,
of wasted foods caused the emission of around 4.4 gigatons of whereas roots and tubers contribute that of 20%, and cereal
greenhouse gas (1). Greenhouse gases are mostly originated from constitutes that of 19% (1, 7). In this review article, two types of
landfill emissions of decaying food, on-farm agriculture emission, agricultural by-products, that is, vegetable and fruit by-products
electricity and heat in the manufacturing process, and the energy are further discussed on their usefulness as functional ingredient
used for agriculture by-products that are lost or wasted. Clearly, and/or foods.
these events can cause the greenhouse effect and lead to global
warming and climate change, which might further affect the Vegetable By-products
extinction of some animal species (3). Vegetable by-products are the secondary products that are often
From the economic perspective, agricultural by-products and discarded or wasted during manufacturing or other stages of food
wastages can affect both the income of farmers and the expenses processing. Up to one-third of vegetables could be wasted in the
of consumers. For example, the cost of food waste is very high, preparation process. Interestingly, certain parts of the vegetables
especially in countries with a high population such as in China are knowingly wasted due to their unfavorable taste or texture.
and the United States of America (4). It is evident as foods For example, vegetable parts, such as hulls, bagasse, and seeds,
worth $32 billion are thrown away yearly in China. Moreover, are mostly discarded in the production line. For certain types of
on average $1,600 worth of food are wasted annually from a vegetables, such as broccoli, cauliflower, and pumpkin, the stem
family of four in the United States of America. These large and leaves are not consumed and thrown away.
amounts of food wastes have a big impact on the income of The seed coat, which is the outer layer that covers the seeds or
farmers (1). In the sub-Saharan Africa, farmers earn only <$2 beans, functions to protect them from external damages (8) and
in a day due to a large amount of postharvest losses. In fact, $940 is one of the vegetable by-products. Seed coats are usually not
billion worth of foods are estimated to be lost or wasted annually, consumed due to the texture and taste, except for some thin seed
and the World Bank estimated $40 million of economic gains coats, such as peanut seed coats. In the canned food industry, seed
could be achieved with just 1% reduction in postharvest losses, coats are discarded in a large quantity as ∼22% of oilseeds and
where this can benefit the small farmers (3). The extremely huge pulses worldwide are lost or wasted annually (1). The wastages
amount of wastage has drawn the attention of researchers to look of oilseeds and pulses are highest in the North Africa, West Asia,
for an alternative of utilizing fruit and vegetable by-products. and Central Asia regions, and these by-products are mostly lost
Therefore, utilizing agricultural by-products not only helps the during the agriculture stage (1).
farmers and economics of customers, but also it can increase Unlike the seed coat, the hull is the hard-protecting cover
food sustainability and reduce food insecurity, especially for of the seeds or grains that protects them during the growing
the underdeveloped countries. This review summarizes different period. Due to their hardness of texture, hulls are removed
types of food developed using fruit and vegetable by-products. before cooking or manufacturing. Globally, hulls contribute to
Through this review article, the potential use of agricultural a large amount of food waste, especially rice hulls due to the high
by-products is explored and discussed. consumption of rice among the Asian countries (9). It is reported
that 30% of the whole cereals are lost, and most of the wastages
are due to human consumption and postharvest activities (1). To
AGRICULTURAL BY-PRODUCTS overcome this problem, hulls are used as a building material, fuel,
and fertilizer (10) as one of the strategies to reduce wastage. Due
Agricultural by-products or wastes are the residues from the to its high content of fiber and protein (11–13), the hull can be an
growing and processing of raw agricultural products, such as alternative source of functional ingredient.
fruits, vegetables, meat, poultry, dairy products, and crops (5). Not all vegetables have peels, unlike fruits. Tubers, gourd,
Moreover, the wastes include animal wastes, such as manure and allium families contain peels, yet they are not normally
and animal carcasses, food processing waste, crop waste, and consumed or used in food preparation. Therefore, vegetable
dangerous and toxic agricultural waste, such as pesticides, peels are often discarded as kitchen or production wastes in the
insecticides, and herbicides. These agricultural wastes can exist manufacturing line. Annually, large amounts of tuber and roots
in the form of liquid, slurry, or solid. are wasted, and up to 5,814,000 tons of tubers and roots are
It is estimated that about 998 million tons of agricultural wasted during the consumption stage in the North America and
wastes are produced annually due to the expanding agricultural Oceania regions. In addition, Europe, North America, Oceania
production. With the drastic demand, there is a significant and industrialized Asia have the highest wastage of roots and
increase in livestock waste, agricultural crop residues, and agro- tubers at the agriculture stage, where ∼45% of tubers and roots
industrial wastes. Hence, the expansion of the farming systems are lost globally (1).
Frontiers in Nutrition | www.frontiersin.org 2 June 2021 | Volume 8 | Article 661693
published: 15 June 2021
doi: 10.3389/fnut.2021.661693
Utilization of Vegetable and Fruit
By-products as Functional Ingredient
and Food
Ke Qi Lau, Mohd Redzwan Sabran* and Siti Raihanah Shafie
Department of Nutrition, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
With the constant growth of the human population, the global demand for food is
increasing annually. Food security is an arising issue due to decreased resources and
massive waste production from the agricultural sector. For example, not all parts of fruits
and vegetables are consumed by consumers, and this phenomenon can lead to huge
amounts of food wastes that are produced globally. Moreover, non-utilized agriculture
by-products, including seed coat, hull, husk, peels, seeds, and pomace, can cause
Edited by: environmental issues. Hence, efficiently utilizing food wastes, such as vegetable and
Juliana Morales-Castro, fruit by-products, could be a way to increase food sustainability, and in line with the
Durango Institute of
Technology, Mexico
United Nations Sustainable Development Goal (SDG) to ensure sustainable consumption
Reviewed by:
and production patterns. Moreover, certain agriculture by-products are reported to
Sapna Langyan, have a high nutritional value and could be potentially used as functional ingredient and
National Bureau of Plant Genetic food in the food industry. This review article summarizes findings on the development
Resources (ICAR), India
Diego A. Moreno, of new functional foods by utilizing different types of agriculture by-products, that
CEBAS-CSIC, Food Science and is, vegetable and fruit by-products as ingredients. Furthermore, the nutritional values,
Technology Department, Spanish
National Research Council, Spain
processing methods, product acceptability, and potential uses of these vegetable and
J. Fernando Ayala-Zavala, fruit by-products are also discussed. These by-products can be an alternative source of
Centro de Investigación en nutrients to support the global demand for functional foods and as one of the strategies
Alimentación y Desarrollo, Consejo
Nacional de Ciencia y Tecnología to cope with food insecurity. Studies have shown that different types of fruit and vegetable
(CONACYT), Mexico by-products were well-incorporated in the development of functional foods, such as
*Correspondence: bakery products and dairy products. Of great importance, this review article provides
Mohd Redzwan Sabran
an insight of the nutritional value, health benefits, and utilization of fruit and vegetable
by-products.
Specialty section:
Keywords: vegetable by-products, fruit by-products, food waste recovery, utilization of food waste, functional
This article was submitted to
food, health benefit, food security
Nutrition and Sustainable Diets,
a section of the journal
Frontiers in Nutrition
INTRODUCTION
Received: 31 January 2021
Accepted: 29 April 2021
In the agriculture field, postharvesting, processing, distribution, and consumption sectors could
Published: 15 June 2021
generate agriculture by-products that are wasted in huge amounts, which can contribute to the
Citation: food waste problem (1). These food wastes are part of unintentional and intentional losses, which
Lau KQ, Sabran MR and Shafie SR
can lead to wastage of agriculture by-products (2). The unintentional losses include inadequate
(2021) Utilization of Vegetable and
Fruit By-products as Functional
farming technologies and lack of proper transportation, whereas the intentional losses include due
Ingredient and Food. to human eating habits. Approximately 45% of fruits and vegetables are wasted worldwide, which
Front. Nutr. 8:661693. is one of the categories with the highest wastage rate (1). The highest agricultural wastage is found
doi: 10.3389/fnut.2021.661693 in Europe, Latin America, North America, and Oceania, and it accounted for ∼10% higher than
Frontiers in Nutrition | www.frontiersin.org 1 June 2021 | Volume 8 | Article 661693
, Lau et al. Vegetable and Fruit By-products
that of industrialized Asia (1). Moreover, the highest production in developing countries increases the global agricultural wastes.
wastage is found in Sub-Saharan Africa, which constitutes It is evident as organic wastes generate up to 80% of the total
∼20% (1). solid wastes in any form, whereas the manure production can
It is of great concern that a massive amount of agricultural by- reach up to 5.27 kg/day/1,000 kg live weight, on a wet weight
products contributes to the food waste problem, subsequently, basis (5). Agriculture by-products are also largely contributed
it can further lead to many environmental and economic issues by the improper utilization of fruits and vegetables that are
(1). According to FAO, food loss and waste is the second highest commonly overproduced seasonally (6). Vegetable and fruit by-
cause of greenhouse gas emission. Statistically, 1.3 billion tons products represent 44% of global food wastes by commodity,
of wasted foods caused the emission of around 4.4 gigatons of whereas roots and tubers contribute that of 20%, and cereal
greenhouse gas (1). Greenhouse gases are mostly originated from constitutes that of 19% (1, 7). In this review article, two types of
landfill emissions of decaying food, on-farm agriculture emission, agricultural by-products, that is, vegetable and fruit by-products
electricity and heat in the manufacturing process, and the energy are further discussed on their usefulness as functional ingredient
used for agriculture by-products that are lost or wasted. Clearly, and/or foods.
these events can cause the greenhouse effect and lead to global
warming and climate change, which might further affect the Vegetable By-products
extinction of some animal species (3). Vegetable by-products are the secondary products that are often
From the economic perspective, agricultural by-products and discarded or wasted during manufacturing or other stages of food
wastages can affect both the income of farmers and the expenses processing. Up to one-third of vegetables could be wasted in the
of consumers. For example, the cost of food waste is very high, preparation process. Interestingly, certain parts of the vegetables
especially in countries with a high population such as in China are knowingly wasted due to their unfavorable taste or texture.
and the United States of America (4). It is evident as foods For example, vegetable parts, such as hulls, bagasse, and seeds,
worth $32 billion are thrown away yearly in China. Moreover, are mostly discarded in the production line. For certain types of
on average $1,600 worth of food are wasted annually from a vegetables, such as broccoli, cauliflower, and pumpkin, the stem
family of four in the United States of America. These large and leaves are not consumed and thrown away.
amounts of food wastes have a big impact on the income of The seed coat, which is the outer layer that covers the seeds or
farmers (1). In the sub-Saharan Africa, farmers earn only <$2 beans, functions to protect them from external damages (8) and
in a day due to a large amount of postharvest losses. In fact, $940 is one of the vegetable by-products. Seed coats are usually not
billion worth of foods are estimated to be lost or wasted annually, consumed due to the texture and taste, except for some thin seed
and the World Bank estimated $40 million of economic gains coats, such as peanut seed coats. In the canned food industry, seed
could be achieved with just 1% reduction in postharvest losses, coats are discarded in a large quantity as ∼22% of oilseeds and
where this can benefit the small farmers (3). The extremely huge pulses worldwide are lost or wasted annually (1). The wastages
amount of wastage has drawn the attention of researchers to look of oilseeds and pulses are highest in the North Africa, West Asia,
for an alternative of utilizing fruit and vegetable by-products. and Central Asia regions, and these by-products are mostly lost
Therefore, utilizing agricultural by-products not only helps the during the agriculture stage (1).
farmers and economics of customers, but also it can increase Unlike the seed coat, the hull is the hard-protecting cover
food sustainability and reduce food insecurity, especially for of the seeds or grains that protects them during the growing
the underdeveloped countries. This review summarizes different period. Due to their hardness of texture, hulls are removed
types of food developed using fruit and vegetable by-products. before cooking or manufacturing. Globally, hulls contribute to
Through this review article, the potential use of agricultural a large amount of food waste, especially rice hulls due to the high
by-products is explored and discussed. consumption of rice among the Asian countries (9). It is reported
that 30% of the whole cereals are lost, and most of the wastages
are due to human consumption and postharvest activities (1). To
AGRICULTURAL BY-PRODUCTS overcome this problem, hulls are used as a building material, fuel,
and fertilizer (10) as one of the strategies to reduce wastage. Due
Agricultural by-products or wastes are the residues from the to its high content of fiber and protein (11–13), the hull can be an
growing and processing of raw agricultural products, such as alternative source of functional ingredient.
fruits, vegetables, meat, poultry, dairy products, and crops (5). Not all vegetables have peels, unlike fruits. Tubers, gourd,
Moreover, the wastes include animal wastes, such as manure and allium families contain peels, yet they are not normally
and animal carcasses, food processing waste, crop waste, and consumed or used in food preparation. Therefore, vegetable
dangerous and toxic agricultural waste, such as pesticides, peels are often discarded as kitchen or production wastes in the
insecticides, and herbicides. These agricultural wastes can exist manufacturing line. Annually, large amounts of tuber and roots
in the form of liquid, slurry, or solid. are wasted, and up to 5,814,000 tons of tubers and roots are
It is estimated that about 998 million tons of agricultural wasted during the consumption stage in the North America and
wastes are produced annually due to the expanding agricultural Oceania regions. In addition, Europe, North America, Oceania
production. With the drastic demand, there is a significant and industrialized Asia have the highest wastage of roots and
increase in livestock waste, agricultural crop residues, and agro- tubers at the agriculture stage, where ∼45% of tubers and roots
industrial wastes. Hence, the expansion of the farming systems are lost globally (1).
Frontiers in Nutrition | www.frontiersin.org 2 June 2021 | Volume 8 | Article 661693
