AU2021104345A4

AU2021104345A4 - A cost-saving and efficient pectin extraction process based on the citrus waste

Info

Publication number: AU2021104345A4
Application number: AU2021104345A
Authority: AU
Inventors: Jianle Chen; Shiguo Chen; Huan CHENG; Donghong LIU; Xingqian YE; Jianwei Zhou
Original assignee: Ningbo University of Technology
Current assignee: Ningbotech University
Priority date: 2021-07-20
Filing date: 2021-07-20
Publication date: 2021-09-16
Anticipated expiration: 2029-07-20

Abstract

Disclosed is a method of cost-saving and efficient recovery of pectin from citrus waste, including the following steps: using the acid processing water from citrus canning as the pectin extractant for fresh citrus fruit peels; filtering the efficient extraction mixture, adding to the resulting filtrate 95% ethanol 1 to 3 times the volume of the filtrate, and then adjusting the pH to a range of 3.5 to 7, followed by standing for 10 minutes to 4 hours; filtering the product after standing, washing the resulting precipitate with 50% to 70% ethanol, and drying and crushing, thereby obtaining the mixed pectin with high yield. The method makes full use of waste resources from citrus fruit canning, solves the problem of pollution, and has the advantages of saving the preparation cost of pectin from citrus peels, and improving the solubility of recovered pectin.

Description

I NINGBOTECH UNIVERSITY AUSTRALIA

Patents Act 1990

INNOVATION SPECIFICATION FOR THE INVENTION ENTITLED "A COST-SAVING AND EFFICIENT PECTIN EXTRACTION PROCESS BASED ON THE CITRUS WASTE"

This invention is described in the following statement:-

A COST-SAVING AND EFFICIENT PECTIN EXTRACTION PROCESS BASED ON THE CITRUS WASTE TECHNICAL FIELD

[0001] The present disclosure belongs to the field of comprehensive utilization of fruit and vegetable canning wastes.

BACKGROUND

[0002] Citrus fruits are probably the best known and most common fruits all over the word. In

2016, the world's citrus planting area was 9453.5 thousand hectares, with the yield of 146.429

million tons. Loose-skin citrus fruits, which are very common, can be processed into canned

citrus fruits. This is a good way to expand the time and space for selling of citrus fruit products,

which not only overcomes the disadvantage of difficult storage and transportation of fruits but

also results in enriched taste of citrus fruit products, improved edibleness, and increased

processing added value of agricultural citrus fruit products.

[0003] The citrus fruit canning process includes the steps of blanching, peeling and separating

into segments, acid-alkali treatment for membrane removing, and rinsing, and features low

resource utilization and high pollution. The acid-alkali treatment step is a process of hydrolyzing

segments with acid and alkali successively to remove the citrus segment membrane, in which the

membrane may be first decomposed and partially softened and dissolved in an acid trough. Thus,

the resulting acid processing water would contain membrane organics dissolved therein and have

a high chemical oxygen demand (COD), approximately 10000 mg/L, and therefore cannot be

discharged directly because it may easily cause pollution such as water eutrophication. The

properties of acid processing water are as follows.

[0004] The acid processing water from citrus segment membrane removal may have a pH of

about 1, about 0.7% of total solids, about 0.1 to 0.3% of pectin, and about 0.07% of total

flavonoids.

-Y

[0005] On the other hand, citrus fruit peels are an important waste resource from citrus fruit canning. For the convenience of storage and transportation of citrus fruit peels, it is currently a

common practice to pre-dry the citrus fruit peels before transportation and sales to downstream

manufacturers that use citrus fruit peels as the raw material for production of dried citrus fruit

peels, essential oil, pectin, etc., with significantly increased processing cost of the citrus fruit

peels due to pre-drying and transportation thereof.

[0006] Citrus fruit peels are one of the main sources of commercial pectin product. Pectin can be widely used as thickener and gelling agent in food processing, which, however, is currently in

short supply. The commercial pectin product can be obtained by the steps of subjecting citrus

fruit peels to drying, crushing and extracting (generally at 70 to 100°C for 1 to 2 hours with an

inorganic acid as extracting agent), as well as filtering, adjusting the pH of the filtrate to a range

of 3.5 to 7, alcohol precipitating (adding food grade ethanol to the filtrate to fully precipitate the

pectin in the filtrate), filtering, drying, etc.

[0007] There have been some reports on the recovery of pectin from citrus fruit canning processing water.

[0008] Chinese invention patent No. CN103122039A discloses a process for recovering pectin

from acid processing water generated during citrus fruit canning, which can be summarized as

pH adjustment of acid discharge water to neutral, followed by preliminary impurity removal by

filtration using a cloth bag, two-step membrane filtration and separation of the filtrate and spray

drying of the separated liquid, thus obtaining the pectin. Another Chinese invention patent

(CN102745836A) discloses a method for treatment of citrus fruit canning production processing

water, which can be summarized as firstly impurity removal by plate-frame pressure filtration

with diatomite, followed by nanofiltration and ultrafiltration after pH adjustment, precipitation of

the resulting concentrate, and centrifuging and drying of the precipitate, thereby obtaining pectin.

A further method that can be used in the precipitation process is salting out. Pectin recovery from

acid processing water, however, may have the problems of relatively low yield, high cost, and

difficult filtration due to fine particles of citrus segment membrane present in the acid processing

water, as well as poor solubility of dried pectin. There is no solution reported so far to on-site

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combined pectin recovery from citrus fruit peels and acid processing water, with cost sharing and

quality improvement of pectin.

SUMMARY

[0009] The present disclosure is intended to provide a method for cost-saving and efficient recovery of pectin from citrus waste. The method can make full use of waste resources from

citrus fruit canning, solve the problem of pollution by processing discharge water and have the

advantages of saving the preparation cost of pectin from citrus fruit peels, reducing the filtering

difficulty of pectin from acid processing water, and improving the solubility of recovered pectin.

[0010] To solve the technical problems as described above, the present disclosure provides a

method for cost-saving and efficient extraction of pectin from citrus waste, including the

following steps:

1) carrying out extraction:

mixing fresh citrus fruit peels with acid processing water from citrus segment

membrane removal (i.e., acid processing water containing components such as

pectin) and stirring at 70 to 95°C for 60 minutes to 100 minutes;

where a pectin extract is obtained from step 1;

2) filtering the pectin extract from step 1, adding to a resulting filtrate 95% (by

volume) ethanol 1 to 3 times the volume of the filtrate, and adjusting pH to a range

of 3.5 to 7, followed by standing (precipitating) for 10 minutes to 4 hours;

3) filtering the product from standing in step 2, washing resulting precipitate with 50%

to 70% (by volume) ethanol once or twice, followed by drying and crushing,

thereby obtaining pectin.

[0011] As an improvement to the method for cost-saving and efficient recovery of pectin from

citrus waste of the present disclosure:

[0012] A ratio of the fresh citrus fruit peels to the acid processing water from citrus segment membrane removal may be 1 g : (10-15) ml.

[0013] As an improvement to the method for cost-saving and efficient recovery of pectin from citrus waste of the present disclosure:

[0014] Mixing the fresh citrus fruit peels with the acid processing water from citrus segment membrane removal and stirring after shearing homogenization.

[0015] As an improvement to method for cost-saving and efficient recovery of pectin from citrus waste of the present disclosure:

[0016] Firstly mixing the fresh citrus fruit peels with the acid processing water from citrus

segment membrane removal in a ratio of 1 g : (1-2) ml, followed by shearing homogenization,

then adding the acid processing water from citrus segment membrane removal until a ratio of the

fresh citrus fruit peels to the total acid processing water from citrus segment membrane removal

is 1 g : (10-15) ml, and finally stirring at 70 to 95°C for 60 minutes to 100 minutes.

[0017] By shearing homogenization, the fresh citrus fruit peels can be crushed to a certain extent,

which is conducive to extraction of pectin from the citrus fruit peels. Such a two-step processing

water addition method can result in improved extraction efficiency from the fresh citrus fruit

peels.

[0018] As an improvement to the method for cost-saving and efficient recovery of pectin from

citrus waste of the present disclosure:

the shearing homogenization may be shearing at 200 r/min for 2 minutes.

[0019] As an improvement to the method for cost-saving and efficient recovery of pectin from

citrus waste of the present disclosure:

the filtering in each of the steps 2) and 3) may be conducted by a 300 to 400-mesh

screen.

V

[0020] As an improvement to the method for cost-saving and efficient recovery of pectin from citrus waste of the present disclosure:

stirring may be carried out while heating at 85°C for 80 to 90 minutes.

[0021] The above-described solution can take into consideration both extraction efficiency and extraction cost.

[0022] As an improvement to the method for cost-saving and efficient recovery of pectin from

citrus waste of the present disclosure.

the step 2 may include: filtering with a 350 to 400-mesh screen, precipitating with 95%

(by volume) ethanol 1 to 2 times the volume of the filtrate, adjusting the pH to 3.5, and standing

(precipitating) for 30 to 45 minutes.

[0023] As an improvement to the method for cost-saving and efficient recovery of pectin from

citrus waste of the present disclosure:

the step 3) may include: filtering with a 350-mesh screen and washing the resulting

precipitate with 60 to 70% (by volume) ethanol.

[0024] The above-described solution can achieve the purpose of cost-efficient washing without

loss of pectin.

[0025] Compared with the prior art, the present disclosure may have the following advantages:

(1) Citrus fruit peels by-product from citrus fruit canning can be used locally for

on-site production without drying and transportation. Without long term storage and

long distance transportation of citrus fruit peels, fresh citrus fruit peels can be

directly used for extraction of pectin, and crushing of dried citrus fruit peels is

omitted. Thus, the difficulty and the duration of pectin extraction process can be

greatly reduced, with significantly saving the cost of citrus peels pre-treatment.

(2) Using acid processing water from citrus segment membrane removal in citrus fruit

canning as pectin extractant for citrus peel extraction, without additional

preparation of extractant, the cost can be obviously reduced without extractant

preparation when compared with commercial pectin production. Besides, the

utilization of the acid processing water from citrus segment membrane removal can

be of great significance for environmental protection.

(3) In combined recovery of pectin from acid processing water from citrus segment

membrane removal and citrus fruit peels, citrus fruit peels with large particles can

act as filter aid to a certain extent, thus resulting in improved filtration over that in

single recovery of pectin from acid processing water.

(4) The pectin obtained by combined recovery can have better solubility due to lowered

pectin aggregation in the combined recovery from acid processing water from citrus

segment membrane removal and citrus fruit peels as compared with that in single

recovery of pectin from acid processing water.

DETAILED DESCRIPTION

[0026] The present disclosure is now further described in conjunction with specific examples,

but the protection scope of the present disclosure is not limited thereto.

[0027] In the present disclosure, sodium hydroxide solution at the concentration of 1% was

employed in pH adjustment. The acid processing water from citrus segment membrane removal

was acid processing water from citrus fruit canning.

Example 1

[0028] Fresh citrus fruit peels from citrus fruit canning were added to the acid processing water

from citrus segment membrane removal in a ratio of 1:10 (g/ml) and then subjected to shearing

at 200 r/min for 2 minutes, stirring while heating at 85°C for 90 minutes, and filtering with a

350-mesh screen. Then, the filtrate was collected and added with 95% ethanol 2 times the

volume of the filtrate (for alcohol precipitation), followed by pH adjustment to 3.5, standing for minutes, precipitation, and separation of precipitate by filtering with a 350-mesh screen. The precipitate was washed with 70% ethanol once (a mass ratio of washing solution used to the precipitate was 2:1), dried (at 40°C for 24 hours), and crushed (60-mesh sieving after the crushing), thereby obtaining pectin.

[0029] The pectin obtained by combined recovery had a yield of 5.9% (based on the wet weight of the citrus fruit peels).

[0030] The pectin extract was filtered at a rate of 760 ml/min per square meter of filter cloth, and

the solubility of pectin reached 91% after the solution stirring for 15 minutes.

Example 2

[0031] Fresh citrus fruit peels from citrus fruit canning were added to the acid processing water

from citrus segment membrane removal such that a ratio of the citrus fruit peels to the acid

processing water was firstly 1:1, and subjected to shearing at 200 r/min for 2 minutes. The acid

processing water from citrus segment membrane removal was then added until the ratio of the

citrus fruit peels to the processing water was 1:10, followed by stirring while heating at 85°C for

minutes and filtering with a 350-mesh screen. Then, the filtrate was collected and added with

% ethanol 2 times the volume of the filtrate, followed by pH adjustment to 3.5, standing for 30

minutes, precipitation, and separation of precipitate by filtering with a 350-mesh screen. The

precipitate was washed with 70% ethanol once, dried and crushed, thereby obtaining pectin.

[0032] The pectin obtained by combined recovery had a yield of 6.2% (based on the wet weight

of the citrus fruit peels).

[0033] The pectin extract was filtered at a rate of 830 ml/min per square meter of filter cloth, and

the solubility of pectin reached 93% after the solution stirring for 15 minutes.

Example 3

[0034] Fresh citrus fruit peels from citrus fruit canning were added to the acid processing water

from citrus segment membrane removal such that a ratio of the citrus fruit peels to the acid processing water was firstly 1:1, and subjected to shearing at 200 r/min for 2 minutes. The acid processing water from citrus segment membrane removal was then added until the ratio of the citrus fruit peels to the processing water was 1:10, followed by stirring while heating at 85°C for minutes and filtering with a 400-mesh screen. Then, the filtrate was collected and added with

% ethanol 1 time the volume of the filtrate, followed by pH adjustment to 3.5, standing for 45

precipitate was washed with 60% ethanol once, dried and crushed, thereby obtaining pectin.

[0035] The pectin obtained by combined recovery had a yield of 6.1% (based on the wet weight

of the citrus fruit peels).

[0036] The pectin extract was filtered at a rate of 800 ml/min per square meter of filter cloth, and the solubility of pectin reached 93% after the solution stirring for 15 minutes.

Example 4

[0037] Fresh citrus fruit peels from citrus fruit canning were added to the acid processing water

processing water was firstly 1:2, and subjected to shearing at 200 r/min for 2 minutes. The acid

citrus fruit peels to the processing water was 1:15, followed by stirring while heating at 85°C for

minutes and filtering with a 400-mesh screen. Then, the filtrate was collected and added with

[0038] The pectin obtained by combined recovery had a yield of 6.2% (based on the wet weight

of the citrus fruit peels).

[0039] The pectin extract was filtered at a rate of 840 ml/min per square meter of filter cloth, and

_U

Comparative Example 1

[0040] This example was the same as example 1 everywhere except for "shearing at 200 r/min for 2 minutes" which was omitted here, and as a result, the pectin obtained by combined

recovery had a yield of 4.9% (based on the wet weight of the citrus fruit peels). The pectin

extract was filtered at a rate of 640 ml/min per square meter of filter cloth, and the solubility of

pectin reached 89% after the solution stirring for 15 minutes.

Comparative Example 2-1

[0041] According to the existing process of obtaining commercial pectin product, fresh citrus fruit peels were subjected to the steps of citrus fruit peels drying, crushing, extraction, alcohol

precipitation, etc. to obtain the commercial pectin product. The process steps and parameters

were specifically as follows: the citrus fruit peels were dried at 50°C for 48 hours, crushed to a

size of about 1 mm, added with hydrochloric acid with pH 1.5 and a ratio of the citrus fruit peels

to the acid of 1:30 for extraction at 85°C for 90 minutes, followed by filtering with a 300-mesh

screen. The filtrate was collected and added with 1 time 95% ethanol, followed by standing for

[0042] As a result, the pectin had a yield of 4.3% (based on the wet weight of the citrus fruit

peels).

[0043] The pectin extract was filtered at a rate of 950 ml/min per square meter of filter cloth, and

[0044] In contrast to the technical solutions of the present disclosure, it was necessary in this

method to pre-dry the citrus fruit peels before crushing and to prepare a hydrochloric acid

solution additionally, leading to greatly increased cost and increased water consumption. Besides,

the method failed to recover pectin from ready-made acid processing water from citrus segment

membrane removal.

Comparative Example 2-2

[0045] The acid processing water from citrus segment membrane removal (i.e., the acid processing water from citrus fruit canning) was directly subjected to the steps of filtering,

alcohol precipitation, drying, crushing, etc. to obtain pectin recovered from acid processing water.

The process steps and parameters were specifically as follows: after filtering with a 350-mesh

screen of the acid processing water from citrus segment membrane removal, the filtrate was

collected and added with 2 times 95% ethanol, followed by pH adjustment to 3.5, standing for 30

[0046] As a result, the acid processing water from citrus segment membrane removal was

filtered at a rate of 590 ml/min per square meter of filter cloth, and the solubility of pectin was

% after the solution stirring for 15 minutes.

[0047] Thus, compared with example 2, a lower filtering rate in single recovery of pectin from

the acid processing water from citrus segment membrane removal and weaker solubility of

pectin due to easy aggregation in single recovery could be observed here.

Comparative Example 3-1

[0048] The ratio of the citrus fruit peels to the processing water was changed from "1:10" as

used in example 2 to "1:5", and the rest was the same with example 2. As a result, the pectin

obtained by combined recovery had a yield of 5.9% (based on the wet weight of the citrus fruit

peels). The pectin extract was filtered at a rate of 740 ml/min per square meter offilter cloth, and

the solubility of pectin reached 92% after the solution stirring for 15 minutes.

Comparative Example 3-2

[0049] The ratio of the citrus fruit peels to the processing water was changed from "1:10" as

used in example 2 to "1:20", and the rest was the same with example 2. As a result, the pectin

obtained by combined recovery had a yield of 6.2% (based on the wet weight of the citrus fruit

peels). The pectin extract was filtered at a rate of 870 ml/min per square meter offilter cloth, and

I /

[0050] In spite of a slightly higher filtering rate over example 2, the time of filtering was dramatically increased due to greatly increased volume of the extract, and the amount of ethanol

used in alcohol precipitation was significantly increased. Therefore, this method would not be

recommended.

[0051] Finally, it should be noted that the examples listed above are merely a few specific examples of the present disclosure. Apparently, the present disclosure would not be limited to the

above examples, and many variations are possible. All modifications that can be directly derived

or conceived by a person of ordinary skill in the art from the specification of the present

disclosure should be regarded as falling into the protection scope of the present disclosure.

Claims

What is claimed is:

1. A method for cost-saving and efficient extraction of pectin from citrus waste, comprising

the following steps:

step 1, carrying out extraction:

mixing fresh citrus fruit peels with acid processing water from citrus segment

membrane removal and stirring at 70 to 95°C for 60 to 100 minutes;

step 2, filtering the mixture from step 1, adding to a resulting filtrate 95 vol % ethanol 1

to 3 times the volume of the filtrate, and adjusting pH to a range of 3.5 to 7, followed by

standing for 10 minutes to 4 hours; and

step 3, filtering the product from standing in step 2, washing a resulting precipitate with

50 vol % to 70 vol % ethanol once or twice, followed by drying and crushing, thereby

obtaining pectin.

2. The method for cost-saving and efficient recovery of pectin from citrus waste according

to claim 1, wherein:

a ratio of the fresh citrus fruit peels to the acid processing water from citrus segment

membrane removal is 1 g : (10-15) ml.

3. The method for cost-saving and efficient recovery of pectin from citrus waste according

to claim 2, wherein:

mixing the fresh citrus fruit peels with the acid processing water from citrus segment

membrane removal and stirring after shearing homogenization;

wherein the shearing homogenization is: shearing at 200 r/min for 2 minutes;

wherein: the filtering in each of the steps 2) and 3) is conducted by a 300 to 400-mesh

screen;

wherein: stirring is carried out while heating at 85°C for 80 to 90 minutes; wherein: the step 2 comprises: filtering with a 350 to 400-mesh screen, precipitating with

95 vol % ethanol 1 to 2 times the volume of the filtrate, adjusting the pH to 3.5, and

standing for 30 to 45 minutes;

wherein: the step 3) comprises: filtering with a 350-mesh screen and washing the

resulting precipitate with 60 to 70 vol % ethanol.

4. The method for cost-saving and efficient recovery of pectin from citrus waste according

to claim 2, wherein:

firstly mixing the fresh citrus fruit peels with the acid processing water from citrus

segment membrane removal in a ratio of 1 g : (1-2) ml, followed by shearing

homogenization, then adding the acid processing water from citrus segment membrane

removal until a ratio of the fresh citrus fruit peels to the total acid processing water from

citrus segment membrane removal is 1 g : (10-15) ml, and finally stirring at 70 to 95°C

for 60 minutes to 100 minutes;

wherein the shearing homogenization is: shearing at 200 r/min for 2 minutes;

screen;

wherein: stirring is carried out while heating at 85°C for 80 to 90 minutes;

wherein: the step 2 comprises: filtering with a 350 to 400-mesh screen, precipitating with

standing for 30 to 45 minutes;

resulting precipitate with 60 to 70 vol % ethanol.