Sweet Corn

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  1. General Requirements
    • 1.1 Grade
    • 1.2 Terminology Used
    • 1.3 Similar Varietal Characteristics
    • 1.4 Packaging
    • 1.5 Sampling Procedures
  2. Size
  3. Shape
  4. Row and Kernel Development
  5. Maturity
    • 5.1 General Requirements
    • 5.2 Definitions
  6. Permanent Defects
    • 6.1 Smut
    • 6.2 Trimming
  7. Condition Defects
    • 7.1 Crushed or Broken Kernels (Bruised Ears)
    • 7.2 Decay
    • 7.3 Husks Freshness
    • 7.4 Presence of Live Worms
    • 7.5 Worm Damage
  8. Tolerances

1. General Requirements

When applying the sweet corn standard as it refers to size, formation, kernel development, etc., the word "ear" should be interpreted to mean the cob portion only.

1.1 Grade

There is only one grade for Sweet Corn: Canada No. 1.

1.2 Terminology

An ear of sweet corn is made up of several parts. The main parts are the shank, husk, silk, cob and kernels.

1.3 Similar Varietal Characteristics

We see several types of sweet corn in our work: White, Golden Bantam, Ornamental and Hybrids. The varieties we normally inspect are now all Hybrids.

Within a package, sweet corn must have similar varietal characteristics. This means that there must be no mixing of white with yellow or Golden Bantam with Hybrids, this is rarely a problem.

1.4 Packaging

Sweet corn must be properly packed. Properly packed in respect of produce that is packed in a container, means that:

  1. the produce is packed in a manner that is not likely to result in damage to the produce during handling or transport,
  2. the container contains not less than the net quantity of produce declared on the label.

When packed in bags, the bags must be of the open mesh type, new, clean and free from stains. Other types of containers must be clean and in good order.

The declaration of net quantity on a container of sweet corn must be declared in half dozen, one dozen or one dozen plus multiples of half dozen except when packed in overwrapped trays, then any count may be packed. Also, where ears of sweet corn are not packed as prepackaged products, the declaration of net quantity may be shown in terms of volume measurement.

1.5 Sampling Procedures

The entire contents of the package or 12 cobs, whichever comes first, should be examined when inspecting sweet corn. In addition, if there are more than one dozen cobs in the package, the inspector must also verify the count marked on the package.

When examining the cob, sufficient leaves should be pulled back on one side to expose enough kernels from top to bottom so that development, maturity, colour, decay, insect damage, etc., are clearly visible. Pulling the husk down an inch or two is not good enough. Suspected specimens should be completely exposed.

2. Size

Canada No. 1 sweet corn must have at least 4 inches of edible kernels and not more than one quarter of the cob may have under-developed or undeveloped kernels.

When packed in a package, cobs which have from 4 to 6 inches of edible kernels must bear the word "Small" in conjunction with the grade. When cobs contain 5 inches or more of edible kernels the word "Large" need not be used.

3. Shape

Canada No. 1 sweet corn must be free from misshapen or stunted ears. Cobs need not be perfectly straight.

In most cases, stunted ears would not likely have enough edible kernel development to make Canada No. 1 grade and the appearance would also be materially affected.

Sweet corn must not have underdeveloped ends. That is to say, ends which have poorly developed kernels or no kernels at all. Any kernel development will likely be small, round, white and very watery, but at times may be flattened and lacking substance (also see Maturity). This type of underdevelopment must not exceed one quarter the length of the cob, even in cases where edible kernels exceed the requirements.

The appearance must not be affected by poorly developed rows of kernels. Rows need not be perfectly straight and may in places have spaces between rows, but rows should not be more crooked than this or have kernels growing out every which way, even if the cob is fairly well filled. (Bear in mind that there is only one grade for this product, so don't look for perfection).

4. Row and Kernel Development

Canada No. 1 sweet corn must have rows that are at least fairly uniform in development. This means that rows may be a bit wavy with slight spaces between at times, but rows or kernels may not be missing, kernels may not be placed every which way or vary in colour or maturity.

5. Maturity

5.1 General Requirements

Maturity can be judged by the thumb test, colour and appearance.

Kernels must be tender, plump and milky. This means that when given the thumb test, the kernels will give off a milky or creamy juice. A thick starchy consistency indicates over maturity, a thin watery consistency indicates under maturity.

The thumb test is done by applying pressure with the thumb nail to kernels about 1/3 the distance down form the tip of the cob.

Kernels in Canada No. 1 sweet corn will be light yellow to golden yellow. Small round whitish kernels could indicate immaturity; dark yellow or golden kernels could be indicative in some varieties of over mature sweet corn. Also if kernels are dented dimpled or tough chewy, in all likelihood the sweet corn is over mature and would fail grade.

5.2 Definitions

The following terms should be used to described maturity:

Immature: Kernels will be small, round, whitish colour, translucent and watery when broken. (This would not meet the maturity requirement).

Tender, Plumo and Milky: Kernels will be well developed, light yellow to golden yellow in colour, and will have juice which is of a milky or creamy consistency.

Turning Hard: Kernels will be slightly dented, or dimpled in appearance, will be dark yellow to orange yellow in colour, the skin will be tough to break and there will be very little juice if any, it will be thick and creamy.

Hard: Kernels will be clearly dented, orange in colour, skins very tough to break and interior of kernels will have a very thick mealy consistency.

6. Permanent Defects

6.1 Smut

Smut is a black fungus growth not often seen these days, but may be found near the top of the ear tip of the cob. Kernels will at first be pink to black and will later develop a dusty fungus which could, under a damp environment, develop into decay. Any amount of smut will be scored.

6.2 Trimming

All loose leaves should be removed and shanks should not be more than 4 inches in length from point of attachment at the butt of the cob. Prepackaged denuded cobs should not show more than 1 inch of shank.

Cobs may be trimmed at the silk end provided at least 4 inches of edible kernels remain and provided all evidence of tapering is not removed.

7. Condition Defects

7.1 Crushed or Broken Kernels (Bruised Ears)

Mechanical harvesters will at times grab the ear above the shank and do some damage to the husk and kernels. This condition is generally manifested by watersoaked patches on the leaves covering an area of crushed and/or broken kernels.

At shipping point score if more than 8 kernels are affected. At destination it would be difficult to say with assurance that this was harvester damage so it could only be scored as a condition defect.

An example of a condition statement for this defect would be as follows: Average 12%, (range from 0 to 22%) of the cobs show crushed or broken kernels, affecting from 9-14 mostly, 10-12 per cob at the shank end. In addition all affected ears show patches on the leaves which are watersoaked in appearance and covering the area affected by crushed or broken kernels.

7.2 Decay

Any amount will be scored whether it is on the cob, silk, husk or butt. Be careful when assessing decay on silk, ensure that it is actually decay and not just wet. Rub the silk between your fingers to see if it is slimy.

7.3 Husks Freshness

Husks must be fresh, green and unbroken.

Fresh: Means of good colour, reasonably moist not dry or wilted. Terms to be used: fresh, slightly wilted, wilted, badly wilted, moist, fairly moist, dry.

Fresh and Green: Means that the husk is dark green and moist to light greenish yellow and fairly moist, but not beige, wilted or dried out. When describing husk colour use the following terms: good green, dark green, green (which could be a dullish green), light green (which could be fading a bit to yellow). These would all satisfy our No. 1 requirements. Turning yellow to yellow, straw coloured, beige or brown colour would not meet our No. 1 requirements at shipping point; this would be a condition defect at destination.

Unbroken: Means that the leaves are not removed to the extent that any of the cob is exposed, although tips may be clipped to remove damage thereby exposing the end of the cob. It is permissible to remove part or all of the husk to expose the kernels so that a consumer can see the quality, but when this is done the cobs must be covered by a transparent wrap to maintain freshness. The usual practice is to denude the whole cob and place it on an overwrapped tray or in a bag.

7.4 Presence of Live Worms

The presence of any live worms, whether on the husk or cob will be scored.

If the worms are "live", treat as a condition defect as the worms may not have been present at shipping point. If the worms are "dead", treat as a permanent defect, since the worms were probably present at shipping point. In cases where there are both "live" and "dead" worms present, treat as a condition defect.

7.5 Worm Damage

Any amount of damage to the cob portion will be scored. Damage on the silk or husk portion would have to materially affect the appearance. Anything affecting over 25% of the surface of the husk, or where silk is badly chewed and entwined in frass.

8. Tolerances

10% of the packages where sweet corn is in packages, may contain:

  1. 10% of the packages where sweet corn is in packages, may contain:
    1. 5% more or less ears than the number of ears marked thereon for packages having a count of 30 or less; and
    2. 2 ears more or less than the number of ears marked thereon for packages having a count of 36 or more;
  2. 15% of the ears by count may exceed the maximum length;
  3. 5% of the ears by count may be below the minimum length;
  4. 1% of the ears by count may be affected by decay;
  5. 5% of the ears by count may have the same grade defect; and
  6. 10% of the ears by count may have grade defects other than those referred to in paragraphs (a) and (b) but including those referred to in paragraphs (c) and (d).
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