8 knowledge points about sweet potatoes

In winter, everyone will fall in love with hot roasted sweet potatoes
.
Recently, some topics about sweet potatoes have attracted attention: Baked sweet potatoes produce a lot of acrylamide? Will baked sweet potatoes made in an air fryer be hot? Can diabetics eat baked sweet potatoes?

Knowledge Point 1

The color of sweet potatoes is what pigment brings

Sweet potatoes belong to a type of
sweet potato.
Sweet potatoes come in a variety of skin and flesh colors, such as pure white, light yellow, orange-yellow, purple, and are called white potatoes, yellow potatoes, sweet potatoes, and purple potatoes, and even purple and white intertwined "flower" potatoes
.
Yellow and orange colors come from carotenoids, specifically β-carotene; The purple color comes from anthocyanins, and in the anthocyanins, the type of cornflower pigment is the majority
.

Knowledge Point 2

How much starch and sugar is in sweet potatoes

There are many varieties of sweet potatoes, some are particularly rich in starch, the starch content is as high as nearly 30%, and the reducing sugar is relatively small, suitable for extracting starch and making noodles
.
Some starch content is between 10%-20%, while reducing sugar content is relatively high, can reach 10%-20%, and the taste is relatively sweet
.
Such sweet potatoes are suitable for fresh food
.

Some scholars have measured 28 sweet potato varieties and found that the soluble sugar of sweet potatoes was between 3.
5% and 7.
0% when they were first harvested.
The starch content varies greatly, between
10% and 31%.

Knowledge Point 3

Why are sweet potatoes sweeter in winter

Soluble sugars are sugars that can be dissolved in water, including glucose, fructose, sucrose, maltose, lactose and other small molecule sugars and fructooligosaccharides
.
For fruits, vegetables and potatoes, the higher the soluble sugar content, the more delicious
it is.

In winter, due to the lower temperature, plants will break down part of the starch into soluble sugars in order to increase osmotic pressure and resist the harm
of low temperature and freezing.
Therefore, after sweet potatoes are stored for a period of time in autumn and winter, the sugar content will increase significantly compared to when they were just harvested, and baked sweet potatoes will be sweeter
.

Knowledge Point 4

Sweet potatoes contain different types of starch

Carbohydrates in sweet potatoes, in addition to sugar, there is starch
.
From a digestive point of view, starch is usually divided into fast-digesting starch, slow-digesting starch and resistant starch
.

Fast-digesting starch can be digested by the body and can quickly raise blood sugar
.
For people with indigestion, fast digestion of starch can reduce the burden on the digestive system and provide energy to the body faster
.
But for people who need to control blood sugar, eating too much fast-digesting starch at once is a big test
.

Slow-digesting starch can also be digested and can slow release energy, but because the digestion rate is slow, the blood sugar rise rate is also slow, which is conducive to postprandial blood sugar stability
.

Resistant starch is likely not digested and absorbed in the small intestine, almost does not raise blood sugar, but enters the large intestine and is decomposed and utilized by microorganisms to produce gas and short-chain fatty acids
.
Small amounts of resistant starch have the benefit of improving intestinal flora and helping to control blood lipids, while large amounts of resistant starch may cause problems such as
gas production, bloating and indigestion.

Raw sweet potatoes can also be eaten, and the reducing sugars in them are digestible
.
However, because the content of resistant starch is higher, the proportion of ingredients that are difficult to digest is larger, and the blood sugar is less raised after meals, and eating too much will cause bloating problems
.

Knowledge Point 5

Sweet potatoes are better absorbed after cooking

Studies have found that steaming sweet potatoes with yellow meat for 35 minutes will slightly reduce the sugar content; Microwave heating for 5 minutes increases the sugar content (compared to the content in the dry weight of the sample).

Boiling also increases the sugar content, but because some of the sugar dissolves in the water, it doesn't feel as sweet
.
The researchers believe that microwave heating may promote the degradation of starch, producing more glucose and maltose
.

Steaming, boiling, and microwave treatment can reduce the proportion of resistant starch in sweet potatoes by more than 60%, and the proportion of fast-digested starch increases from less than 10% to more than
30% in raw sweet potatoes.
When boiling and microwave processing, the proportion of slow-digesting starch is reduced from 8% to less than 1% in raw sweet potatoes, however, the slow-digesting starch retention rate of steamed sweet potatoes is high, reaching about
7%.

Therefore, when eating sweet potatoes cooked, most of the starch can be digested, plus the reducing sugars in it, will increase the blood sugar response
.
In contrast, when cooking and microwave cooking, the blood sugar may be raised faster
.
However, microwave cooking also has an unexpected benefit, with carotene levels increasing by nearly 1 times
after cooking.
In fact, this is not a strange thing, it may be because the combination of carotene and protein is broken down after microwave cooking, and it can be better released from the cell, so the actual amount will increase
.

Knowledge Point 6

Nutritional differences in sweet potatoes of different colors

Studies have found that the taste and taste of sweet potatoes are positively correlated
with the β-carotene content, protein and starch content.
That is to say, for yellow flesh sweet potatoes, the more orange and yellow the color, the more delicious
.
For purple-fleshed sweet potatoes, the higher the anthocyanin content, the less delicious it is; The higher the sugar content, the tastier
it will be.

Scientists analyzed the color and composition of 28 kinds of raw sweet potatoes and found that the total polyphenol content was 28-117 mg/100 grams, among which purple potato varieties were significantly higher than yellow meat varieties
.
Carotene content is 0-9.
8 mg/100 g
.
Eating sweet potatoes with orange-yellow flesh is a great way
to supplement with carotene.

The assay also found that purple sweet potato had a strong inhibitory effect on trypsin activity, and the higher the polyphenol content, the more advanced
the inhibition of protease.
This can explain why purple sweet potatoes are prone to stomach congestion and bloating after eating too much, which is quite unfriendly
to patients with indigestion and gastrointestinal diseases.

Knowledge Point 7

Whether baked sweet potatoes contain acrylamide

Baked sweet potatoes, like baked potatoes, fried potatoes, etc.
, will produce acrylamide in cooking and processing at more than 120 °C, of which 160 °C-180 °C acrylamide has the largest
output.
And this temperature range is exactly the temperature
used when the food is baked and fried.
However, compared to french fries, baked sweet potatoes still have a much
lower acrylamide content.

Chinese scientists measured 7 baked sweet potato samples, and their acrylamide content was 33-201 μg/kg; For 7 fries samples, the results ranged from 364 to 587 μg/kg
.
This is because compared with sweet potatoes, potatoes have a higher protein content, a stronger Maillard reaction, and a higher
content of amino acids such as glutamine, which is easy to form acrylamide.

Acrylamide is not a highly toxic substance, and when present in small amounts, it does not significantly affect health
.
Most residents in our country do not eat baked and fried dishes every day, nor eat bread, biscuits, cakes and other baked pasta every day, and occasionally eat a baked sweet potato is not worried
.

Knowledge Point 8

Do air fryer roasted sweet potatoes make people catch fire

Some netizens said that after eating baked sweet potato chips and baked potato strips made by the air fryer, they would feel a little hot, manifested as dry mouth, sore throat, and even acne
on the face.
There may be two main reasons
for this.

On the one hand, baked food (including air fryers) has a low moisture content, and when eating, chewed dry food will absorb a large amount of water from saliva, oral mucosa and throat, resulting in local dehydration of the mucosa, dry discomfort
.
Dry and hard food fragments are easy to cause small wounds to the mucosa, coupled with the decline in resistance after dehydration of the mucosa, it is easy to lead to bacterial infection and inflammation, and pain and discomfort
in the mouth and throat.

On the other hand, baked food produces substances that promote inflammatory response during high-temperature heating, referred to as "pro-inflammatory components"
.
These include some products of the Maillard reaction, such as acrylamide, which is a pro-inflammatory component
.
AGEs, the terminal products of the Maillard reaction, are also pro-inflammatory factors
.
The more crispy and browned the roast, the higher
the content of these pro-inflammatory substances.

If the temperature is too high, polycyclic aromatic hydrocarbons, oil oxidation polymerization products, these are all things
that promote the inflammatory response.
Eating too much of the pro-inflammatory ingredients can also trigger acne or make acne worse
.
If you find yourself having an adverse reaction to these overly crispy foods, fried, smoked, roasted, air-fried foods need to be eaten less, and sweets should also be eaten less, because they also promote inflammation
.
When eating, eat more raw fruits and vegetables to match it
.

(Edited by Li Chuang)