Impact of selected process parameters on crust flaking of frozen partly baked bread

Dust formation in French fries

In this study we report on the analysis of dust formation, a quality problem arising in the industrial processing of par-fried, frozen french fries. This dust constitutes fractured pieces broken off the crust during finish frying. We claim that this dust problem has many similarities with flaking arising during the final-baking of par-baked french baguettes, i.e. the two problems are governed by the same physical principles. Inspired by the hypotheses behind flaking, we have made an experimental design, where we have perturbed the operating conditions of an industrial processing line of french fries. The measured dust during finish frying is correlated with the physical properties of the crust, measured in the different unit operations of the industrial processing line, and the operating conditions. We have shown that dust is non-linearly correlated to 1) the moisture content of the crust as influenced by drying and par-frying, and 2) the freezing rate in the industrial tunnel freezer. Remarkably, the amount of dust decrease with the increase of frozen storage time, which we have explained via viscoelastic relaxation of locked-in stress - mediated by moisture migrating from core to crust. This decay is shown to be independent of pretreatments, which only determines its starting value. With the given relations industry can in principle control the dust problem, but these measures have to be weighed against their effects on other objectives of the industry.

3D Characterization of Sponge Cake as Affected by Freezing Conditions Using Synchrotron X-ray Microtomography at Negative Temperature

In this study, the microstructural evolution of a non-reactive porous model food (sponge cake) during freezing was investigated. Sponge cake samples were frozen at two different rates: slow freezing (0.3 °C min⁻¹) and fast freezing (17.2 °C min⁻¹). Synchrotron X-ray microtomography (µ-CT) and cryo-scanning electron microscopy (Cryo-SEM) were used to visualize and analyze the microstructure features. The samples were scanned before and after freezing using a specific thermostated cell (CellStat) combined with the synchrotron beamline. Cryo-SEM and 3D µ-CT image visualization allowed a qualitative analysis of the ice formation and location in the porous structure. An image analysis method based on grey level was used to segment the three phases of the frozen samples: air, ice and starch. Volume fractions of each phase, ice local thickness and shape characterization were determined and discussed according to the freezing rates.

The Impact of Parbaking on the Crumb Firming Mechanism of Fully Baked Tin Wheat Bread

The impact of parbaking on the quality and shelf life of large tin bread baked from 270 g of wheat flour was investigated using a proton nuclear magnetic resonance method combined with techniques that measure at different length scales. With increasing partial baking time, the resilience of fresh partially baked crumb increased because of its more extended amylose and gluten networks. During subsequent storage, the crumb became more firm due to an increased extent of amylopectin retrogradation and moisture redistribution. Although only amylopectin retrogradation was reversed during final baking, a fresh fully baked (FB) bread with reversed crumb softness was obtained. Furthermore, the rate of crumb firming during final storage of FB bread was not higher than that of conventionally baked bread. This was attributed to the high crumb to crust ratio of large tin bread which caused the crumb moisture content to remain sufficiently high despite nonreversible moisture redistribution during intermediate storage.

Effect of proving time on the quality of frozen pre-baked French style rolls elaborated with the addition of wholegrain flour and enzymes

Proving is a step in the breadmaking process that can be crucial in determining the final characteristics of the product presented to the consumer. The objective of this work was to evaluate the effect of proving time on the quality of frozen pre-baked French style rolls elaborated with the addition of wholegrain flour and enzymes. With this objective, doughs from six different formulations were allowed to ferment to different stages of proving. The first stage corresponded to the stage where the dough presented the maximum point of volume development without losing its resistance to touch. The second stage was soon after the first one, being characterized by a loss of resistance to touch but without a marked loss of volume. The rolls were evaluated for their specific volume, crumb texture (firmness and springiness), oven spring, shape, cut opening and cut height. The results showed that the proving time influenced various characteristics of the pre-baked French bread. A longer proving time tended to result in greater specific volume of the rolls with greater crumb springiness, but with a less firm crumb and reduced cut opening and cut height. The oven spring and shape were not altered by the proving time. The increase in volume was the result of increases in the width and length of the rolls. This study showed that the proving time was one of the factors responsible for the collapse in the structure of the pre-baked rolls, and that an adequate formulation could overcome the loss in cut opening and cut height resulting from a longer proving time.