Hubbard Foods Limited of Auckland makes a variety of oats-based value-added products. In the preparation of a range of products at Hubbard Foods, technical staff has become aware of a bitterness problem that sporadically appears in toasted oats. Toasting involves dry heating to about 150°C resulting in the golden colour and flavour development necessary for range of products. Bitterness development has been described in the literature, but Hubbard staff is necessarily focussed on production issues, rather than on a sporadic problem seemingly outside the scope of production variables. The author of this thesis set out to identify the cause and suggest a remedy. Prior research with oats has shown that bitterness and associated off-flavours are linked to the accumulation of free fatty acids, their volatile oxidation products, and possibly amino acids and certain phenols. Oats are distinguished from related grains by their high relative fat content, about seven percent, and an associated very active lipase. The free fatty acids stem from the lipase activity that should be, but may not be, inactivated at source in Australia. This is achieved in the milling process by physical disruption and moist heating to a temperature at which the enzyme is denatured. However, residual lipase activity may adversely affect oats quality during time in storage and transit. A number of analytical methods for cereals were adapted to match the constraints of time and resources. These methods were for colour, moisture, peroxidase activity, p-anisidine, and fat and free fatty acids content, composition of fatty acids, total phenols, volatiles, and bitterness as perceived by an analytical sensory panel of four people. Determination of lipase activity is very expensive, so peroxidase activity is commercially used as an indicator. If the latter is inactive, the former will necessarily be also inactive.The designed methods were first applied to 17 oats lots passing through the Hubbard environment, where 14 were paired raw and toasted. The values of moisture, fat content, free fatty acids content and total phenols were within the normal limits expected for commercial lots of oats compared with the previous studies. Not much variation was observed among the 17 oats lots, with the exception of lot DWHE25. Lot DWHE25 was a faulty product, which had high moisture content, high free fatty acids content, and tasted very bitter. The results suggested that moisture content, free fatty acids and bitterness were usually correlated. In spite of the differences encountered and the clues provided by extremes, the data generated from Hubbard oats lots did not provide enough variation in quality to lead to a definitive chemical model of bitter flavour development. But perhaps crucially, it was found that most samples as received from Hubbard Foods were peroxidase-active which conflicted with the results reported on specification sheets prepared by the oats supplier. These specifications accompanied each lot delivered to Hubbard Foods. Therefore, the supplier’s method was examined and was found to be deficient in one critically important respect. Their method omitted the key reactant hydrogen peroxide. Therefore, it is possible that the lipase was active in many of the samples. Therefore, some experiments were conducted where raw oats, from Hubbard Foods and a supermarket, were treated with water additions and stored for a period to examine the effect of moisture content on the quality and flavour deterioration on subsequent storage. Water-treated oats were toasted to simulate a typical Hubbard process, yielding a total of 58 samples with carrying moisture contents. The data set was statistically analysed to identify the cause of bitterness and the means of its control. The free fatty acids content, volatile compounds particularly hexanal, and total phenols increased with moisture content and storage time. The correlations between chemical analysis and sensory test indicated that free fatty acids positively correlated with bitterness (r = 0.71), and hexanal was also positively correlated. Total phenols did not appear to correlate with bitterness. Oats lots with high peroxidase activity tended to have the poorest quality, strongly implicating residual lipase activity as the critical factor. There were no important interactions between water addition and toasting for most of the experiments. Therefore, it seems likely that the toasting procedures at Hubbard Foods are not responsible for bitterness formation. The cause(s) of bitterness is certainly at source, with a faulty peroxidase test strongly implicated.
FAQs
The cause of bitter flavour development in toasted rolled oats (Avena sativa L.)? ›
Prior research with oats has shown that bitterness and associated off-flavours are linked to the accumulation of free fatty acids, their volatile oxidation products, and possibly amino acids and certain phenols.
Why are my baked oats bitter? ›If the dry ingredients are not well mixed, there can be pockets or lumps of ingredients (especially leavening) that can lead to bitter or off flavors.
Why is oat flour bitter? ›Sensory-directed fractionation of extracts prepared from oat flour (Avena sativa L.) followed by LC-TOF-MS, LC-MS/MS, and 1D/2D-NMR experiments revealed avenanthramides and saponins as the key phytochemicals contributing to the typical astringent and bitter off-taste of oat.
Why do rolled oats taste so bad? ›Oatmeal tastes bad because it often has a slightly bitter flavor, which is due to the acridness of the natural fatty acids in oats. The good news is that oatmeal can be spruced up with any number of toppings and flavors.
Does toasting oats make them taste better? ›How to Upgrade a Basic of Oatmeal. The solution is simple: Give the raw oats a quick toasting. This will add depth, complexity, and a rich caramel-like flavor to your oats without having to toss in any additional ingredients.
Why do my rolled oats taste bitter? ›Prior research with oats has shown that bitterness and associated off-flavours are linked to the accumulation of free fatty acids, their volatile oxidation products, and possibly amino acids and certain phenols.
Why does my oatmeal taste old? ›That said, the quality of the oats will decline over time, and they may become stale, change color, or develop flavors that aren't particularly palatable. If dry oats are exposed to moisture while stored, they'll be more susceptible to mold growth.
Do I need to add baking powder to oat flour? ›*Steel-cut oats will yield four cups of oat flour. Oat flour doesn't contain gluten, so you may need to add other ingredients (like baking powder/soda in combination with apple cider vinegar or lemon juice) to help create a light and fluffy texture.
What makes flour taste bitter? ›One of the telltale signs of old or stale whole wheat flour is its bitter taste. As the bran in the flour becomes rancid, it imparts an unpleasant bitterness to your baked goods. This bitterness can overpower the natural flavors of your recipes and leave a less-than-pleasant aftertaste.
What does oat flour do to your body? ›Health Benefits of Oats
The recommended diet for weight loss is rich in dietary fiber. Oat flour is rich in fiber which is an incredible carbohydrate because it increases metabolism, triggers your CCK hormone that signals to your brain that you're full, absorbs fat, and promotes regular bowel movements.
What not to mix with oatmeal? ›
Whatever you do, steer clear of the worst offenders: dried fruit with added sugars, like Craisins or dried pineapple. "These are almost always made with added sugar, if not also an artificial sweetener, says Pennsylvania-based RD Gina Consalvo. "Always choose a fresh fruit instead." Need hard proof?
What are the negatives of rolled oats? ›Oats can cause gas and bloating. To minimize side effects, start with a low dose and increase slowly to the desired amount. Your body will get used to oat bran and the side effects will likely go away.
What happens if you eat too many rolled oats? ›Oats are a good source of carbohydrates and overeating may lead to an increase in your weight. As it is bland in nature, overconsuming oats may lead to an increase in sugar intake. Opting for an oats-only diet may deprive your body of getting nourishment from other healthy food sources.
What is the best way to toast oats? ›It's simple. Follow these steps: Add raw oats to a dry skillet and heat the pan over medium. Toast the oats, stirring occasionally until they turn golden brown and smell slightly nutty, about two minutes.
How do you make rolled oats taste good? ›Adding nutritious toppings to oatmeal can boost its flavor and contribute to its health benefits. Try adding fruit for sweetness, veggies or eggs for a savory twist, or sources of protein and fat to make it a balanced meal.
Why you should always toast the oats for your oatmeal? ›Toasting your oats before making oatmeal elevates their flavors and texture by adding deep, browned flavors. Browning happens when heat, amino acids, and sugars react with each other, creating new flavor compounds in foods and adding caramelized, roasted, meaty, and/or sweet notes.
What makes cookies bitter? ›Baking soda helps cookies spread outward and upward while cooking. Adding too little can cause flat, lumpy cookies. Adding too much can lend a bitter taste to the cookies.
Why are my baked oats gummy? ›Oats absorb moisture as they sit—so if you let your batter sit before you bake, you'll run the risk of making a dense, thick, gummy baked oatmeal (when you really want a light, fluffy one), she explains.
Why do my overnight oats taste bad? ›While overnight oats are a healthy breakfast option, they can taste bland if you don't add any sweetener. Some people skip the sweetener altogether, thinking that the fruit they add will be enough. However, a little bit of honey, maple syrup, or brown sugar can go a long way in making your oats more enjoyable.