Understanding the acid value in bread and its influencing factors

This article delves into the significance of Acid Value (AV) in baked goods, emphasizing its role as an indicator of product quality. It explores factors influencing AV, such as ingredient selection, processing methods, and storage conditions.

Novonesis lab tests reveal insights into how key ingredients and additives impact AV. Furthermore, the use of lipases in recipes is discussed, highlighting Novonesis' lipase platform's efficacy in maintaining AV while enhancing baking outcomes.

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Girl enjoying fresh and quality bread with low acid value

What does Acid Value (AV) mean?

During the processing and storing of oils and fats, triglycerides undergo hydrolysis, leading to the production of free fatty acids. A surplus of free fatty acids can signal lower level of freshness in the product, but often other factors such as high temperature, humidity, damaged packaging, or microbial contamination are underlying causes.

A minor increase in free fatty acids doesn't significantly affect the quality of the product or consumers' health. Yet, exceedingly high fatty acid content combined with oxidation can cause an unpleasant odor in baked products and have adverse health effects.

The Acid Value (AV), reflecting the increment of free fatty acids (FFA), is a crucial parameter in food product specifications. Essentially, AV is the amount of potassium hydroxide (KOH) in milligrams required to neutralize organic acids present in 1 gram of food samples. Various countries or regions (like the EU, US, Japan, China) and organizations such as JECFA, ISO include acid value in their food standards.

What role does AV
play in baked goods?

In the production of baked goods, including bread, different oil and fat products like edible oil, butter, margarine, and emulsifiers are used as raw materials.

Besides these, factors such as process control and storage can influence the product's acid value. Given the logistical challenges faced by baked goods producers in distributing their products across large geographic regions such as China, maintaining product quality becomes essential.

Acid value helps assess the overall hygiene and quality of baked goods containing the aforementioned raw materials. Therefore, it serves as a key parameter in national standards for these products. As per China's national standard GB 7099-2015, the acid value of bread and pastry products should not exceed 5 mg/g. The standard also imposes limits on peroxide value as another indicator of oil/ fat oxidation.

What factors influence AV in baked goods, and how does this affect formulation?

As per China's national standard, the method for determining the AV in baked goods is outlined in GB 5009.229-2016 - Food safety national standard acid value determination in food. This method involves using a KOH (potassium hydroxide) or NaOH (Sodium hydroxide) standard solution with a titration method to measure the acid value of the test sample.

The calculation of AV includes not just the free lipid acid from oil/fat hydrolysis but also other acids such as naturally inherent lipid acid from raw materials (like lipid in wheat flour, emulsifiers, butters, etc.) and other organic acids produced by yeast fermentation (like lactic acid, acetic acid, etc.). These acidic components, extracted from test samples, react with either KOH or NaOH and get factored into the final acid value results.

This is why, the ingredients that go into your formulation are important; they have a direct impact on the final products' acid value. Additionally, the baking process may induce variations in the acid value. Products with a long shelf life have even more factors at play, such as transportation and storage.

What do Novonesis lab tests show when it comes to AV in baked goods?

Baking experts at Novonesis have conducted extensive tests to evaluate how ingredients, additives, processing, and storage can impact the acid value.

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How do key ingredients affect AV?

From below table 1, it is evident that ingredient selection impacts the final acid value of bread. Butter yields a relatively higher acid value compared to shortening, possibly due to the latter's stability after undergoing hydrogenation and interesterification.

The content of oil/fat also significantly affects the final product, with a clear correlation between increasing shortening content and acid value.

The impact of different wheat flours on bread acid values is not as pronounced, likely due to the low oil content in wheat flour and the stability of its lipid composition.

Table 1: Impact of key raw materials on bread’s acid value

Ingredients	Dosage	Bread Acid Value (mg/g)
Butter (AV 4.5 mg/g used for trial)	8%	1.00
Shortening (AV 0.9 mg/g used for trial)	0%	0.95
	4%	0.98
	8%	1.30
Flour Typ 1 (AV 10 mg/g)	-	1.80
Flour Typ 2 (AV 19 mg/g)	-	1.70
Emulsifiers	Dosage	Bread Acid Value (mg/g)
DATEM (AV 70 mg/g used for trial)	0.2%	1.70
CSL (AV 68 mg/g used for trial)	0%	1.30
CSL (AV 68 mg/g used for trial)	0.05%	1.80

*The acid value is analyzed after 10 days storage at 25°C

Emulsifiers are widely used in breadmaking to enhance texture and mouthfeel. Given their lipid acid functional group, they can increase bread's acid value. From table 1, it can be seen that adding 0.05% CSL will lead to an increase in acid value of 0.5 mg/g in the final product acid value, which is rather significant.

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How do process and storage conditions affect AV?

The fermentation method and storage conditions can also impact bread's acid value. We analyzed bread samples’ acid value from the two most commonly used fermentation methods in China.

The sponge and dough fermentation process, with its longer fermentation time, releases more organic acid thus increasing the bread's acid value (0.92 mg/g*), especially compared to rapid fermentation (0.06 mg/g*).

While storage time and temperature don't significantly impact the acid value – even at high temperatures like 38°C – one can see that microbial contamination during storage can cause a surge in the acid value (see AV at 25°C and 30 days).

Table 2: Impact of process and storage on bread’s acid value

Storage temperature	Storage duration	Acid value* mg/g
25°C	10 days	1.1
25°C	20 days	1.1
25°C	30 days	29.5
38°C	20 days	0.72

*Based on the same basic recipe. The acid value is analyzed after 10 days storage at 25°C.

How does the use of
lipases affect AV?

Lipases, including phospholipases, are widely used in various baking products. These enzymes catalyze the hydrolysis of triglycerides or phospholipids in flour to form monoglyceride, lysophospholipid, or other hydrolysates. Compared to the naturally occurring lipid structure, these hydrolysates tend to be more amphipathic, with a long hydrophobic tail and a hydrophilic area post enzyme hydrolysis.

This new structure resembles artificially-synthesized emulsifiers like Distilled Glycerin Monostearate (DMG), Sodium Stearyl Lactate (SSL) and Diacetyl Tartaric Acid Ester of Mono- and Diglycerides (DATEM). This indicates that a treatment with lipases creates an in-situ emulsification effect in baked products, leading to significant improvements in dough operability, final product texture, and whiteness. Consequently, lipases have gained substantial recognition from baking and flour improvers, particularly for products without a high addition of exogenous oil or fat.

Although lipase catalysis of oil or fat components can lead to the release of free amino acids and potentially increase the acid value, particularly when exogenous oils or fats are added to provide more substrates for lipase function, this increase can be managed effectively. From a practical perspective, the right selection and application of enzymes can keep this increase within acceptable limits.

Why use Novonesis lipases in your recipes?

At Novonesis, we offer a broad lipase platform that caters to your different needs. If you’re located in a region with heightened concerns around acid value, we've screened and identified the best-in-class lipases that minimally impact this parameter.

In breads that use shortening as an ingredient, our lipases barely affect acid values, further demonstrating our commitment to providing solutions that meet your quality and health standards while enhancing the baking experience – refer to table 3 to see how. Similarly, there is a very limited impact on the acid value across shelf-life – refer to table 4 for further data.

However, in breads that incorporate butter as an ingredient, determining the impact of lipase treatment becomes challenging. This is because butter alone can introduce significant variations in the acid value.

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Quality baked buns on tray in a baking production facility

Table 3: Impact of lipase on acid value of breads made with shortening

Recipe shortening 8%	Lipase dosage	Acid value 1 week
Control flour 1	0	1.8
Lipopan^® Xtra	15ppm	1.8
Control flour 2	0	1.7
Lipopan^® Xtra	15ppm	1.8

Table 4: Impact of lipase on acid value of breads that have 14 days shelf-life

Type	Lipase dosage	Acid value (mg/g) Day 1	Acid value (mg/g) Day 14
Control	0	2.1	2.1
Lipopan^® Prime	30ppm	1.4	1.5
Lipopan^® Xtra	20ppm	2.3	1.9
Lipopan^® F	20ppm	2.6	2.7

Too long; didn’t read? Here’s what you need to know…

The acid value in bread is determined by a combination of factors, including the selection of ingredients (like flour and oil/fat), additives, processing aids (such as emulsifiers and enzymes), as well as the chosen baking process and storage conditions. Ensuring an acceptable acid value level is a systematic task, requiring careful ingredient selection, process control, and storage management.

While lipase treatment theoretically could increase the acid value, its impact can be minimized by selecting the appropriate enzyme and using it in the correct dosage.

At Novonesis, we offer a range of high-quality lipases with proven effectiveness in strengthening dough and improving texture. We also provide specific solutions designed to minimize the impact on acid value and reduce compliance risks. Moreover, through continual innovation, the potential of lipases to reduce your dependency on emulsifiers is paving the way towards a more robust, health-conscious, and sustainable baking ecosystem.

^{_{Meet the author:}}
Mingzhu Wang
Baking Application Manager, China

I have a background in food science and nutrition along with 13 years’ working experience in the food and beverages industry. I joined Novozymes in 2014, now known as Novonesis.

My passion is developing enzyme and microbe application solutions for customers across various food industries including protein, plant-based ingredients, dairy, functional food, and baking. I strive to enable better and more sustainable foods through biosolutions.