This invention relates to commercial methods for adding fruit or similar flavors to yogurt, and more particularly, to techniques for filling containers with "sundae-style" yogurt, in which a top layer of fruit preserves overlies yogurt in the bottom of a container, and in which the fruit preserves are immediately inside a lid which closes the top of the container.
Yogurt is a very nutritious dairy product which generally contains cultures of two bacteria (Lactobacillus bulgaricus and Streptococcus themophilus) that aid in the digestive process. In addition to the basic nutritional value of plain yogurt, a vast number of consumers will only eat yogurt that is fruit flavored, rather than plain yogurt.
At the present time, fruit flavored yogurt is commonly sold in several styles, including a "fruit-on-the-bottom" style in which a layer of fruit preserves is on the bottom of the container and the yogurt fills the rest of the container, or Swiss style yogurt in which fruit preserves are folded into pre-set, stabilized batch-processed yogurt.
The usual procedure for producing fruit-on-the-bottom yogurt is to initially inject, under pressure, approximately 11/2 ounces of fruit preserves onto the bottom of an empty container on a high speed (120 units per minute) filling line. Immediately thereafter, the remainder of the container is filled with a bacteriologically inoculated, gum stabilized liquid milk, after which the filled container is closed with a removable opaque lid. The filled containers are then cased and incubated for a period of 4 to 8 hours so that fermentation of the culture in the liquid milk produces yogurt. The containers of yogurt are then refrigerated to coagulate or solidify the stabilizers in the yogurt, and the containers are finally shipped to retail stores or markets.
A variety of animal and/or vegetable gum stabilizers are commercially added to the inoculated liquid milk solution to provide a commercially desirable increase in the viscosity of the yogurt upon incubation and subsequent refrigeration. Such stabilizers have been used in fruit-on-the-bottom and Swiss style fruit flavored yogurt.
Stabilizers such as modified corn or tapioca starch are also added to the fruit preserve layer to inhibit bacteria in the yogurt from attacking sugars in the fruit preserve layer.
Fruit-on-the-bottom yogurt suffers from a number of disadvantages. There is a major unwillingness on the part of consumers, many of whom are children, to stir up the fruit from the bottom of the container, or to eat only plain yogurt until reaching the fruit preserve layer at the bottom of the container. Further, during storage, there is an essentially unavoidable "wheying out" of the liquid whey fraction of the yogurt, in which some of the whey naturally present in the yogurt separates from the yogurt and seeps to the bottom of the container. In fruit-on-the-bottom yogurt, the whey that seeps into the bottom of the container reduces the effectiveness of the stabilizers in the fruit layer and dilutes the fruit preserves, converting the fruit layer to an unattractive soupy mass, as well as disrupting the natural flavor of the fruit preserves.
Prior to this invention, it was not thought possible to commercially produce a container of sundae-style yogurt in which a top layer of fruit preserves is supported above the yogurt. The inoculated liquid milk fraction, with or without added stabilizers, is a watery solution, even after the incubation step produces yogurt (i.e., prior to refrigeration). The milk or yogurt fraction has a lower specific gravity than the fruit preserves, and therefore the milk or yogurt fraction (prior to refrigeration) will not support a top layer of fruit preserves. The fruit preserves sink to the bottom of the container. Hence, it has become a standard practice in the industry to prepare and market fruit-on-the-bottom yogurt.