In the national standard of "Packaging General Terms", packaging is clearly defined: "Packaging is the overall name of containers, materials and auxiliary materials used in accordance with certain technical methods to protect goods in the circulation process, facilitate storage and transportation, and promote sales." It also refers to the operational activities in which certain technical methods are applied in the process of using containers, materials and auxiliary materials to achieve the above purposes. "[1] With the development of packaging machinery and modern science and technology, packaging technology is becoming more and more advanced, and more and more able to meet the needs of modern packaging industry. At this stage, many industries have emerged advanced packaging technology, such as sensory packaging, functional packaging, intelligent packaging and so on. As the future development needs of agricultural products, accelerating and promoting modern packaging of agricultural products will become the inevitable choice of our current economic development.
1 Packaging of fruits, vegetables and agricultural products
1.1 Fruit packaging
With the improvement of living standards and health awareness, consumers' demand for fruit is also increasing. However, compared with Europe and America, our fruit supply chain and marketing methods are still in the infancy and development stage. Our fruit in the major production areas of the base, the traditional way of sale still exists, no packaging, direct truck level from the farm to the city, roadside car hawking or fruit stores for unpackaged sales.
Now the Internet new economy, new e-commerce rapid development, China's urbanization rate has exceeded 60%, all kinds of hypermarkets emerge in an endless stream, e-commerce platform competition intensified, consumers for all kinds of fruit options increased, thus the demand for product packaging more demanding. Because a good packaging, attracted the attention of the people, improve everyone's desire to buy, but also promote the sales of fruit, and even improve the product grade and profit space. At the same time, a suitable outer packaging, accelerate the circulation and sales of fruit, reduce the loss of fruit, greatly improve the income of fruit farmers, promote the development of society.
1.2 Vegetable packaging
Similar to fruit packaging, fresh vegetables in China, from the origin to the wholesale markets in cities and towns, and then to the farmers' markets around the country, in this process, either no packaging, or textile bag packaging, in the process of transportation and transportation, vegetables due to lack of protection caused by a lot of crushing rot, loss and loss.
In the retail sector, vegetables are subject to secondary pollution due to the lack of corresponding packaging protection. In recent years, large supermarkets, hypermarkets, and large e-commerce platforms have emerged as box-type purchase or distribution models, vegetable selection, removal of damaged and deteriorated parts; Wash, cut, and sell in small packages. Since the outbreak of the epidemic last year, the urban community vegetable online distribution market capacity has expanded rapidly, and the prospect is quite impressive, a large e-commerce platform to enter this emerging field of competition, all kinds of creative fruit and vegetable packaging emerge in endlessly, see Figure 1.
Figure 1 shows creative fruit and vegetable packaging
Agricultural packaging containers include: plastic packaging containers, paper packaging containers, wood packaging containers, metal packaging containers and fiber packaging containers. Because paper packaging has the following advantages: 1), both light and can protect goods; 2), easy to print text description, promote the sale of goods; 3), easy to carry, low cost, easy to sell. Thus, paper packaging containers have become the mainstay of traditional fruit and vegetable packaging materials, which account for about 45% of the total output value of packaging.
2 Requirements for packaging containers for fruit and vegetable agricultural products
GB/T 34343-2017 "General Technical Requirements for Packaging Containers of Agricultural Products Logistics" [2] Requirements for paper packaging containers: Packaging containers of fruit and vegetable agricultural products should have shock-proof and shock-proof functions. Corrugated boxes for the packaging of fruit and vegetable agricultural products should be stapled corrugated boxes. It is recommended to use metal stapling wire with a width of more than 1.5mm, and the stapling must be treated with rust prevention. Nail wire should not have rust, peeling, cracking and other quality problems; Nail joint should be nailed firmly, nailed through, there should be no overlapping nails, warp nails and other defects.
3 Requirements for packaging materials for fruit and vegetable agricultural products
GB/T 34344-2017 "General Technical Requirements for Packaging Materials of Agricultural Products Logistics" [3] Requirements for carton packaging materials of agricultural products are as follows: box cardboard, corrugated cardboard, honeycomb cardboard and other materials should be selected; Packaging should have light weight, good air permeability and folding performance, printing performance; The packaging materials of fruit and vegetable cartons should be corrugated cardboard; The amount of harmful mineral fillers should be controlled during the processing of corrugated base paper, and the content must meet the requirements of relevant national laws, regulations and standards; Carton board shall comply with GB/T 13024; Corrugated base paper shall comply with the provisions of GB/T 13023; Honeycomb paperboard shall comply with BB/T 0016; Corrugated cardboard shall comply with the provisions of GB/T 6544.
3.1 Corrugated base paper
Corrugated base paper refers to the wrapping paper used for the production of corrugated board core layer, that is, the base paper material used to form corrugated corrugated board. It is heated by corrugating roller in corrugating production line.
According to GB/T 13023-2008 "Corrugated core (original) paper" [4], its technical indicators should meet the requirements of Table 1.
Table 1 Technical specifications of corrugated core (original) paper
| Index name | unit | Lv. | Superior product | First grade goods | Qualified product |
| quantify（80、90、100、110、120、140、160、180、200） | g/m2 | AAA | （80、90、100、110、120、140、160、180、200）±4% | （80、90、100、110、120、140、160、180、200）±5% | |
| AA | |||||
| A | |||||
| compactness | g/cm3 | AAA | ≥0.55 | ≥0.50 | ≥0.45 |
| AA | ≥0.53 | ||||
| A | ≥0.50 | ||||
Lateral ring pressure index ≥140 g/m2～180 g/m2 ≥180 g/m2 | N•m/g | AAA | ≥7.5 |
≥5.0 ≥5.3 ≥6.3 ≥7.7 |
≥3.0 ≥3.5 ≥4.4 ≥5.5 |
| ≥8.5 | |||||
| ≥10.0 | |||||
| ≥11.5 | |||||
| AA | ≥7.0 | ||||
| ≥7.5 | |||||
| ≥9.0 | |||||
| ≥10.5 | |||||
| A | ≥6.5 | ||||
| ≥6.8 | |||||
| ≥7.7 | |||||
| ≥9.2 | |||||
| Flat pressure index a | N•m2/g | AAA | ≥1.40 | ≥1.00 | ≥0.80 |
| AA | ≥1.30 | ||||
| A | ≥1.20 | ||||
| Longitudinal fracture length | km | AAA | ≥5.00 | ≥3.75 | ≥2.50 |
| AA | ≥4.50 | ||||
| A | ≥4.30 | ||||
| Water absorption should not exceed | g/m2 | — | 100 | — | — |
| Delivery moisture | % | AAA | 8.0±2.0 | 8.0±2.0 | 8.0±3.0 |
| AA | |||||
| A | |||||
3.2 Carton Board
Box board for the manufacture of corrugated board for non-coated box board, non-bleached pulp lined box board. It is mainly divided into three types of cow's leather box board with pure wood pulp or more than 80% wood pulp, cow's leather lined box board and ordinary box board made without sulfate wood pulp (with waste paper lined). Pure wood pulp is very little in the country, mainly imported, the domestic production of cowhide noodles is increasing year by year this year, ordinary box cardboard is the largest variety, such as the more popular fruit carton, carton packaging.
According to GB/T 13024-2016 "Box Board" [5], its technical indicators shall comply with the provisions of Table 2.
Table 2 Technical specifications of cartons of cardboard
| Transverse short distance compression indexIndex name | unit | Superior product | First grade goods | Qualified product | |
| Quantitative a | g/m2 | 90.0±4.0 100±5 110±6 125±7 160±8 180±9 200±10 220±10 250±11 280±11 300±12 320±12 340±13 360±14 | |||
| Banner weight difference | Width ≤1600mm Width > 1600mm | % | ≤6.0 | ≤7.5 | ≤9.0 |
| ≤7.0 | ≤8.5 | ≤10.0 | |||
| compactness |
≤220 g/m2 ＞220 g/m2 | g/m3 | ≥0.70 | ≥0.68 | ≥0.60 |
| ≥0.72 | ≥0.70 | ≥0.60 | |||
| Burst resistance index |
＜125 g/m2 (125～160)g/m2 (160～200)g/m2 (200～250)g/m2 (250～300)g/m2 ≥300 g/m2 | kPa•m2/g | ≥3.50 | ≥3.10 | ≥1.85 |
| ≥3.40 | ≥3.00 | ≥1.80 | |||
| ≥3.30 | ≥2.85 | ≥1.70 | |||
| ≥3.20 | ≥2.75 | ≥1.60 | |||
| ≥3.10 | ≥2.65 | ≥1.55 | |||
| ≥3.00 | ≥2.55 | ≥1.50 | |||
| Lateral ring pressure index |
＜125 g/m2 (125～160)g/m2 (160～200)g/m2 (200～250)g/m2 (250～300)g/m2 ≥300 g/m2 | N•m/g | ≥8.50 | ≥6.50 | ≥5.00 |
| ≥9.00 | ≥7.00 | ≥5.30 | |||
| ≥9.50 | ≥7.50 | ≥5.70 | |||
| ≥10.0 | ≥8.00 | ≥6.00 | |||
| ≥11.0 | ≥8.50 | ≥6.50 | |||
| ≥11.5 | ≥9.00 | ≥7.00 | |||
| Smoothness (front) | s | ≥8 | ≥5 | — | |
| Lateral folding resistance | 次 | ≥60 | ≥35 | ≥6 | |
| Water absorption (positive/negative) | g/m2 | ≤35.0/50.0 | ≤40.0/100.0 | ≤60.0/— | |
| Delivery moisture | % | 8.0±2.0 | 9.0±2.0 | ||
| Transverse short distance compression indexb | ＜250 g/m2 | N•m/g | ≥21.4 | ≥19.6 | ≥18.2 |
| ≥250 g/m2 | ≥17.4 | ≥16.4 | ≥14.2 | ||
a Can also produce other quantitative box board. b Horizontal short distance compression index is not used as an assessment index. | |||||
3.3 Corrugated cardboard
Corrugated cardboard refers to a composite cardboard used to make corrugated boxes by one or more layers of corrugated paper bonded between one or more layers of paper or cardboard. The corrugated corrugated board is arranged in a row with each other and supports each other to form a triangular or waveform structure, which has good mechanical properties such as compression, bending and buffering. The corrugated structure and size of UV corrugated cardboard should meet the requirements of Table 3.
For the thickness of corrugated board: the thickness of single corrugated board should be higher than the lower limit of the corresponding corrugated height specified in Table 3; The thickness of multi-layer corrugated cardboard shall be higher than the sum of the lower limits specified in Table 3.
Table 3 Corrugated structure and size of corrugated board
| Corrugated form | Corrugated height h/mm | Width t/mm | Corrugated number/(PCS /300mm) |
| A | 4.5～5.0 | 8.0～9.5 | 34±3 |
| C | 3.5～4.0 | 6.8～7.9 | 41±3 |
| B | 2.5～3.0 | 5.5～6.5 | 50±4 |
| E | 1.1～2.0 | 3.0～3.5 | 93±6 |
| F | 0.6～0.9 | 1.9～2.6 | 136±20 |
Corrugated board is divided into single corrugated board (S), double corrugated board (D) and three corrugated board (T). According to GB/T 6544-2008 "Corrugated Board" [6], its technical indicators should meet the requirements of Table 4.
Table 4 Technical specifications of corrugated cardboard
| designation | Corrugated board minimum comprehensive quantity/(g/m2) | Superior product | Qualified product | ||||
| Class designation | Breaking strength(not less than) /kPa | Side pressure strength (not less than) /(kN/m) | Class designation | Breaking strength (not less than) /kPa | Side pressure strength (not less than) /(kN/m) | ||
| S | 250 | S-1.1 | 650 | 3.00 | S-2.1 | 450 | 2.00 |
| 320 | S-1.2 | 800 | 3.50 | S-2.2 | 600 | 2.50 | |
| 360 | S-1.3 | 1000 | 4.50 | S-2.3 | 750 | 3.00 | |
| 420 | S-1.4 | 1150 | 5.50 | S-2.4 | 850 | 3.50 | |
| 500 | S-1.5 | 1500 | 6.50 | S-2.5 | 1000 | 4.50 | |
| D | 375 | D-1.1 | 800 | 4.50 | D-2.1 | 600 | 2.80 |
| 450 | D-1.2 | 1100 | 5.00 | D-2.2 | 800 | 3.20 | |
| 560 | D-1.3 | 1380 | 7.00 | D-2.3 | 1100 | 4.50 | |
| 640 | D-1.4 | 1700 | 8.00 | D-2.4 | 1200 | 6.00 | |
| 700 | D-1.5 | 1900 | 9.00 | D-2.5 | 1300 | 6.50 | |
| T | 640 | T-1.1 | 1800 | 8.00 | T-2.1 | 1300 | 5.00 |
| 720 | T-1.2 | 2000 | 10.00 | T-2.2 | 1500 | 6.00 | |
| 820 | T-1.3 | 2200 | 13.00 | T-2.3 | 1600 | 8.00 | |
| 1000 | T-1.4 | 2500 | 15.50 | T-2.4 | 1900 | 10.00 | |
3.4 Honeycomb Cardboard
Honeycomb cardboard because of its light weight, high flat compression strength, good cushioning performance and seismic performance, while in sound insulation, safety, recycling and reuse has better advantages, is a low-cost green packaging buffer material, it is especially suitable for transportation packaging valuable, heavy, vulnerable goods, such as home appliances, mechanical and electrical products.
According to BB/T0016-2018 "Honeycomb Paperboard for Packaging Materials" [7], its flat compression strength value should not be lower than the provisions of Table 5.
Table 5 Technical indicators of packaging materials Honeycomb paperboard Unit: kPa
| Honeycomb board thickness | Honeycomb side length | |||||||
| 6 mm | 8 mm | 10 mm | 12 mm | 14 mm | 16 mm | 18 mm | 20 mm | |
| 5 mm | 300 | 248 | 218 | 198 | 184 | 173 | 165 | 158 |
| 8 mm | 296 | 246 | 216 | 196 | 181 | 170 | 162 | 155 |
| 10 mm | 290 | 240 | 210 | 190 | 175 | 164 | 155 | 150 |
| 15 mm | 286 | 236 | 205 | 185 | 170 | 160 | 152 | 145 |
| 20 mm | 280 | 230 | 200 | 180 | 165 | 155 | 145 | 140 |
| 25 mm | 278 | 230 | 205 | 178 | 163 | 153 | 144 | 137 |
| 30 mm | 277 | 227 | 197 | 177 | 162 | 152 | 143 | 136 |
| 40 mm | 275 | 225 | 195 | 175 | 160 | 150 | 141 | 134 |
| 50 mm | 272 | 220 | 172 | 157 | 132 | 127 | 119 | 112 |
4 Common quality problems in the packaging of fruit and vegetable agricultural products
4.1 Packaging base paper quality does not meet the requirements
Such as base paper weight difference; Paper grade (rupture index, ring pressure index, folding resistance) confusion; Whiteness, color fastness and other non-compliance with contract or standard requirements, other related jerry-cutting behavior.
4.2 The physical specifications of the package do not meet the standards
Common indicators such as corrugated cardboard edge compression strength, corrugated carton empty box compressive strength, corrugated cardboard rupture resistance, surface color printing wear-resistant performance, paper absorbability are lower than standard requirements.
4.3 Large printing color difference
The same batch of paper packaging, there are different shades of color; The color difference between different suppliers of the same variety is obvious; Color fluctuation exists in different batches of packaging from the same supplier.
4.4 Other quality defects
The film is not smooth, the glazing effect is not good, the overprinting is not allowed, the tongue is false sticky or glue overflow, the text content is leaked, the pressure line is cracked or shallow, the folding performance is poor, the die cutting dislocation, the skylight is off, the handle is broken or out, and so on.
The final packaging quality problem is the finished carton damage, deformation, color difference, fading, wear and other product packaging quality problems. The result is sales complaints, reduced consumer desire to buy, and declining sales in the product market.
5 Fruit and vegetable agricultural products packaging testing technology
5.1 Sample taking and treatment
The samples were processed according to GB/T 450 and the processing according to GB/T 10739. Standard atmospheric conditions: The optimal environmental conditions are temperature of (23±1) ℃ and relative humidity of (50±2) %.
5.2 Quantitative and banner quantitative difference
Quantification is a basic physical index, and its level and uniformity directly affect the physical strength, mechanical, optical and printing properties of paper, cardboard and corrugated cardboard. Quantitative and price related, the purchase of base paper is calculated by weight, and the accounting of carton, cardboard production enterprises is calculated by unit area. The quantitative determination is carried out in accordance with the provisions of GB/T 451.2. The circular quantitative sampler is used to accurately cut 10 samples with an area of 100cm2, weigh the mass with a suitable scale, and then multiply by 10 to determine the quantity of the sample.
The banner quantification difference is the ratio of the difference between the maximum and minimum values of the sample banner quantification to the mean value of the sample quantification, expressed as a percentage (%). Banner quantitation difference was measured at GB/T 451.2.
5.3 Tightness
Measured according to GB/T 451.3. The thickness of the sample is measured by the paper and paperboard thickness tester, divided by the quantity, and the tightness value is calculated.
5.4 Transverse ring pressure index
The ring compression strength of the base paper affects the compressive strength of the corrugated box. The transverse ring pressure index was measured according to GB/T 2679.8. First, the ring pressure sampler is used, and then the thickness is measured with the thickness measuring instrument. Then, the appropriate test center plate is selected according to the thickness, and the sample is loaded. The center plate of the loaded sample is placed in the middle position of the lower pressure plate of the compression strength tester.
5.5 Flat pressure index
The flat pressure index of base paper was determined according to GB/T 2679.6.
5.6 Longitudinal fracture length
The longitudinal fracture length was determined in accordance with the provisions of GB/T 12914-2018.
5.7 Water Absorption
Water absorption mainly affects the moisture resistance of corrugated boxes. Water absorption was measured according to GB/T 1540.
5.8 Delivery moisture
Delivery moisture shall be subject to GB/T 462.
5.9 Rupture resistance and rupture index
Rupture resistance refers to the pressure exerted by the hydraulic system when the elastic film breaks the maximum pressure of the circular area of the paper pattern, expressed in kilopascals (kPa). The break resistance index is the break resistance divided by the quantity expressed in kPa.m2/g. The break resistance of box board directly affects the break resistance of corrugated board. The breakage of paper and cardboard is determined by the paper breakage tester according to GB/T454, and the breakage of corrugated cardboard is determined by the paper breakage tester according to GB/T1539.
5.10 Lateral folding resistance
According to the folding resistance of the transverse cutting sample is the horizontal folding resistance. The transverse folding resistance mainly affects the folding resistance of the carton shake lid. The transverse folding resistance of the carton cardboard is measured according to the MIT folding resistance method of GB/T 457, and the initial tension is 9.8N, which can be tested with the MIT folding resistance tester.
5.11 Side pressure strength
The edge compression strength directly affects the compressive performance of corrugated boxes. The edge pressure strength is measured according to GB/T 6546.
5.12 Bonding strength
Adhesion strength according to GB/T 6548. The national standard stipulates that the bonding strength of any bonding layer of corrugated cardboard should not be less than 400N/m, in order to find the weakest link of corrugated cardboard.
5.13 Flat compression strength
The testing of flat compression strength of honeycomb paperboard shall be carried out according to BB/T0016-2006.
This paper was published in Hunan Packaging magazine in April 2021
